WO2009117599A2 - Shielded three-terminal flat-through emi/energy dissipating filter - Google Patents

Shielded three-terminal flat-through emi/energy dissipating filter Download PDF

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Publication number
WO2009117599A2
WO2009117599A2 PCT/US2009/037700 US2009037700W WO2009117599A2 WO 2009117599 A2 WO2009117599 A2 WO 2009117599A2 US 2009037700 W US2009037700 W US 2009037700W WO 2009117599 A2 WO2009117599 A2 WO 2009117599A2
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WO
WIPO (PCT)
Prior art keywords
emi
shielded
energy dissipating
filter
flat
Prior art date
Application number
PCT/US2009/037700
Other languages
French (fr)
Other versions
WO2009117599A3 (en
Inventor
Robert A. Stevenson
Buehl E. Truex
Richard L. Brendel
Christine A. Frysz
Warren S. Dabney
Haytham Hussein
Jose Luis Lorente Adame
Robert Shawn Johnson
Scott Brainard
Original Assignee
Greatbatch Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Greatbatch Ltd. filed Critical Greatbatch Ltd.
Priority to EP09723163.3A priority Critical patent/EP2269200B1/en
Priority to CN2009801189056A priority patent/CN102037528A/en
Priority to JP2011500962A priority patent/JP2011517970A/en
Publication of WO2009117599A2 publication Critical patent/WO2009117599A2/en
Publication of WO2009117599A3 publication Critical patent/WO2009117599A3/en

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    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/18Applying electric currents by contact electrodes
    • A61N1/32Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372Arrangements in connection with the implantation of stimulators
    • A61N1/375Constructional arrangements, e.g. casings
    • A61N1/3752Details of casing-lead connections
    • A61N1/3754Feedthroughs
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/02Details
    • A61N1/08Arrangements or circuits for monitoring, protecting, controlling or indicating
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/18Applying electric currents by contact electrodes
    • A61N1/32Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/362Heart stimulators
    • A61N1/37Monitoring; Protecting
    • A61N1/3718Monitoring of or protection against external electromagnetic fields or currents
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/18Applying electric currents by contact electrodes
    • A61N1/32Applying electric currents by contact electrodes alternating or intermittent currents
    • A61N1/36Applying electric currents by contact electrodes alternating or intermittent currents for stimulation
    • A61N1/372Arrangements in connection with the implantation of stimulators
    • A61N1/375Constructional arrangements, e.g. casings
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00Fixed capacitors; Processes of their manufacture
    • H01G4/35Feed-through capacitors or anti-noise capacitors
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00Fixed capacitors; Processes of their manufacture
    • H01G4/40Structural combinations of fixed capacitors with other electric elements, the structure mainly consisting of a capacitor, e.g. RC combinations
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01RELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R13/00Details of coupling devices of the kinds covered by groups H01R12/70 or H01R24/00 - H01R33/00
    • H01R13/66Structural association with built-in electrical component
    • H01R13/719Structural association with built-in electrical component specially adapted for high frequency, e.g. with filters
    • H01R13/7195Structural association with built-in electrical component specially adapted for high frequency, e.g. with filters with planar filters with openings for contacts
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H1/00Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
    • H03H1/0007Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network of radio frequency interference filters
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H7/00Multiple-port networks comprising only passive electrical elements as network components
    • H03H7/01Frequency selective two-port networks
    • H03H7/17Structural details of sub-circuits of frequency selective networks
    • H03H7/1741Comprising typical LC combinations, irrespective of presence and location of additional resistors
    • H03H7/1766Parallel LC in series path
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61NELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00Electrotherapy; Circuits therefor
    • A61N1/02Details
    • A61N1/08Arrangements or circuits for monitoring, protecting, controlling or indicating
    • A61N1/086Magnetic resonance imaging [MRI] compatible leads
    • HELECTRICITY
    • H01ELECTRIC ELEMENTS
    • H01GCAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G4/00Fixed capacitors; Processes of their manufacture
    • H01G4/002Details
    • H01G4/018Dielectrics
    • H01G4/06Solid dielectrics
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H1/00Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
    • H03H2001/0021Constructional details
    • H03H2001/0042Wound, ring or feed-through type capacitor
    • HELECTRICITY
    • H03ELECTRONIC CIRCUITRY
    • H03HIMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
    • H03H1/00Constructional details of impedance networks whose electrical mode of operation is not specified or applicable to more than one type of network
    • H03H2001/0021Constructional details
    • H03H2001/0085Multilayer, e.g. LTCC, HTCC, green sheets
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00Printed circuits
    • H05K1/18Printed circuits structurally associated with non-printed electric components
    • H05K1/181Printed circuits structurally associated with non-printed electric components associated with surface mounted components
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/10Details of components or other objects attached to or integrated in a printed circuit board
    • H05K2201/10007Types of components
    • H05K2201/10015Non-printed capacitor
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K5/00Casings, cabinets or drawers for electric apparatus
    • H05K5/0091Housing specially adapted for small components
    • H05K5/0095Housing specially adapted for small components hermetically-sealed
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K9/00Screening of apparatus or components against electric or magnetic fields
    • HELECTRICITY
    • H05ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05KPRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K999/00PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS dummy group
    • H05K999/99PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS dummy group dummy group

Definitions

  • the present invention relates generally to feedthrough filter capacitor EMI filters. More particularly, the present invention relates to a hybrid EMI filter substrate and/or flex cable assembly which embody embedded shielded flat- through/feedthrough filters and/or energy dissipating circuit elements. This invention is applicable to a wide range of connectors, terminals and/or hermetic seals that support lead wires as they ingress/egress into electronic modules or shielded housings. In particular, the present invention applies to a wide variety of active implantable medical devices (AIMDs). [Para 2] FIGURES 1 -40 provide a background for better understanding the significance and novelty of the present invention.
  • FIGURE 1 illustrates various types of active implantable and external medical devices 1 00 that are currently in use.
  • FIG. 1 is a wire formed diagram of a generic human body showing a number of implanted medical devices.
  • 1 0OA represents a family of hearing devices which can include the group of cochlear implants, piezoelectric sound bridge transducers and the like.
  • I OOB represents a variety of neurostimulators and brain stimulators. Neurostimulators are used to stimulate the Vagus nerve, for example, to treat epilepsy, obesity and depression.
  • Brain stimulators are pacemaker-like devices and include electrodes implanted deep into the brain for sensing the onset of the seizure and also providing electrical stimulation to brain tissue to prevent the seizure from actually occurring.
  • the lead wires associated with a deep brain stimulator are often placed using real time MRI imaging. Most commonly such lead wires are placed during real time MRI.
  • 10OC shows a cardiac pacemaker which is well- known in the art.
  • 1 0OD includes the family of left ventricular assist devices (LVAD's), and artificial hearts, including the recently introduced artificial heart known as the Abiocor.
  • 1 0OE includes an entire family of drug pumps which can be used for dispensing of insulin, chemotherapy drugs, pain medications and the like. Insulin pumps are evolving from passive devices to ones that have sensors and closed loop systems. That is, real time monitoring of blood sugar levels will occur. These devices tend to be more sensitive to EMI than passive pumps that have no sense circuitry or externally implanted lead wires.
  • 10OF includes a variety of bone growth stimulators for rapid healing of fractures.
  • 1 0OG includes urinary incontinence devices.
  • 1 0OH includes the family of pain relief spinal cord stimulators and anti-tremor stimulators.
  • 10OH also includes an entire family of other types of neurostimulators used to block pain.
  • 1001 includes a family of implantable cardioverter defibrillators (ICD) devices and also includes the family of congestive heart failure devices (CHF). This is also known in the art as cardio resynchronization therapy devices, otherwise known as CRT devices.
  • ICD implantable cardioverter defibrillators
  • CHF congestive heart failure devices
  • This is also known in the art as cardio resynchronization therapy devices, otherwise known as CRT devices.
  • 1 00J illustrates an externally worn pack. This pack could be an external insulin pump, an external drug pump, an external neurostimulator or even a ventricular assist device.
  • 10OK illustrates the insertion of an external probe or catheter.
  • 10OL illustrates one of various types of EKG/ECG external skin electrodes which can be placed at various locations.
  • I OOM are external EEG electrodes placed on the head.
  • FIGURE 2 is a prior art unipolar discoidal feedthrough capacitor, which has an active internal electrode plate set 102 and a ground electrode plate set 1 04.
  • the inside diameter termination surface 106 is connected electrically to the active electrode plate set 1 02.
  • An outside diameter termination surface 108 is both solderable and electrically conductive, and it is connected to the outside diameter of electrode plate sets 104.
  • FIGURE 3 is a cross-section of the discoidal feedthrough capacitor of FIG. 2 shown mounted to a hermetic seal 1 1 2 of an active implantable medical device (AIMD).
  • AIMD active implantable medical device
  • the lead wire 1 1 4 is continuous.
  • the hermetic seal 1 1 2 is attached to, typically, a titanium housing 1 1 6, for example, of a cardiac pacemaker.
  • An insulator 1 1 8, like alumina ceramic or glass, is disposed within a ferrule 1 20 and forms a hermetic seal against body fluids.
  • the terminal pin or lead wire 1 14 extends through the hermetic seal 1 1 2, passing through aligned passageways through the insulator 1 1 8 and the capacitor 1 10.
  • a gold braze 1 22 forms a hermetic seal joint between the terminal pin 1 14 and the insulator 1 1 8.
  • Another gold braze 1 24 forms a hermetic seal joint between the alumina insulator 1 1 8 and the titanium ferrule 1 20.
  • a laser weld 1 26 provides a hermetic seal joint between the ferrule 1 20 and the housing 1 1 6.
  • the feedthrough capacitor 1 10 is shown surface mounted in accordance with U.S. Patent 5,333,095, and has an electrical connection 1 28 between its inside diameter metallization 1 06 and hence the active electrode plate set 102 and lead wire 1 1 4. There is also an outside diameter electrical connection 1 30 which connects the capacitor's outside diameter metallization 108 and hence the ground electrodes 1 04 to the ferrule 1 20.
  • Feedthrough capacitors are very efficient high frequency devices that have minimal series inductance. This allows them to operate as EMI filters over very broad frequency ranges.
  • FIG. 3 one can see that another way to describe a prior art discoidal feedthrough capacitor 1 1 0 is as a three-terminal capacitor. Three-terminal devices generally act as transmission lines. Referring to FIG. 3, one can see that there is a current "i" that passes into lead wire 1 1 4.
  • i current
  • lead wire 1 1 4 On the body fluid side there is generally an implanted lead which can undesirably act as an antenna which can pick up energy from environmental emitters. This energy is known as electromagnetic interference (EMI).
  • EMI electromagnetic interference
  • Cell phones, microwave ovens and the like have all been implicated in causing interference with active implantable medical devices.
  • this interference enters lead wire 1 1 4 at point X (FIG.3), it is attenuated along its length by the feedthrough capacitor 1 1 0.
  • the undesirable high frequency EMI has been cleaned off of the normal low frequency circuit current (such as pacemaker pacing pulses or biologic frequency sensors) so that the high frequency EMI has been significantly attenuated.
  • Another way of looking at this is as the high frequency energy passes from terminal 1 to terminal 2 (FIGS. 3 and 4), it is diverted through the feedthrough capacitor 1 1 0 to the ground terminal which is also known as the third terminal or terminal 3.
  • the feedthrough capacitor 1 1 0 also performs a two other important functions: a) its internal ground electrodes 1 02 and 1 04 act as a continuous part of the overall electromagnetic shield housing of the electronic device or module which physically blocks direct entry of high frequency RF energy through the hermetic seal 1 1 2 or equivalent opening for lead wire ingress and egress in the otherwise completely shielded housing (such RF energy, if it does penetrate inside the shielded housing can couple to and interfere with sensitive electronic circuitry), and; b) the feedthrough capacitor 1 10 very effectively shunts undesired high frequency EMI signals off of the lead wires to the overall shield housing where such energy is dissipated in eddy currents resulting in a very small temperature rise.
  • FIGURE 4 is a schematic diagram showing the discoidal feedthrough capacitor 1 10 previously described in connection with FIGS. 2 and 3. As one can see, it is a three-terminal device consistent with terminals 1 , 2 and 3 illustrated in FIG. 3.
  • FIGURE 5 is a quadpolar prior art feedthrough capacitor 1 32 which is similar in construction to that previously described in FIG. 2 except that it has four through holes.
  • FIGURE 6 is a cross-section showing the internal electrodes 1 02, 104 of the capacitor 1 32 of FIG. 5.
  • FIGURE 7 is a schematic diagram showing the four discrete feedthrough capacitors comprising the quadpolar feedthrough capacitor 1 32 of
  • FIGURE 8 is an exploded electrode view showing the inner and outer diameter electrodes of the unipolar feedthrough capacitor 1 10 of FIGS. 2 and 3. One can see the active electrode plates set 1 02 and the ground electrode plate set 104. Cover layers 1 34 are put on the top and bottom for added electrical installation and mechanical strength.
  • FIGURE 9 is an exploded view of the interior electrodes of the prior art quadpolar feedthrough capacitor 1 32 previously illustrated in FIG. 5. As shown in FIG. 9, the active electrode plate sets are shown as 1 02 and the ground electrode plates are shown as 104. Cover layers 1 34 serve the same purpose as previously described in connection with FIG. 8.
  • FIGURE 10 illustrates a prior art quadpolar feedthrough capacitor
  • Wire bond pads 1 38, 1 38', 1 38", 1 38'" and 1 40 are shown for convenient connection to the internal circuitry of the
  • FIGURE 1 1 is a cross-section taken generally from section 1 1 -1 1 from FIG. 10.
  • the internal circuit traces Ti through T 4 to the wire bond pads 1 38-1 38'" are shown.
  • FIGURE 1 2 is a schematic diagram of the prior art wire bond pad quadpolar hermetic feedthrough 1 32 of FIG. 1 0.
  • FIGURE 1 3 is a prior art monolithic ceramic capacitor (MLCC) 142. These are made by the hundreds of millions per day to service the consumer electronics and other markets. Virtually all cell phones and other types of electronic devices have many of these.
  • the MLCC 1 42 has a body 144 generally consisting of a high dielectric constant ceramic such as barium titinate. It also has solderable termination surfaces 1 46 and 1 48 at either end. These termination surfaces 1 46 and 1 48 provide a convenient way to make a connection to the internal electrode plates of the MLCC capacitor 142.
  • FIG. 1 3 can also take the shape and characteristics of a number of other types of capacitor technologies, including rectangular, cylindrical, round, tantalum, aluminum electrolytic, stacked film or any other type of capacitor technology.
  • FIGURE 14 is a sectional view taken from section 1 4-1 4 in FIG. 1 3.
  • the left hand electrode plate set is shown as 1 50 and the right hand electrode plate set is shown as 1 52.
  • the opposite electrode plate set (or right hand plate set) 1 52 is shown connected to the external metallization surface 148.
  • prior art MLCC and equivalent chip capacitors are also known as two-terminal capacitors. That is, there are only two ways electrical energy can connect to the body of the capacitor. In FIGS. 1 3 and 1 4, the first terminal "1 " is on the left side and the second terminal "2" is on the right side.
  • FIGURE 1 5 is an ideal schematic diagram of the prior art MLCC capacitor 1 42 of FIG. 1 3.
  • FIGURE 1 6 is a more realistic schematic diagram showing the fact that the MLCC 1 42 structure as illustrated in FIG. 1 3 has series inductance L.
  • This inductive property arises from the fact that it is a two-terminal device and does not act as a transmission line. That is, its lead wires and associated internal electrodes all tend to add series inductance to the capacitor. It is well known to electrical engineers that MLCC capacitors will self-resonate at a particular frequency.
  • FIGURE 1 7 gives the formula for this resonant frequency. There is always a point at which the capacitive reactance as shown in FIG. 1 6 is equal and opposite to the inductive reactance. It is this point that these two imaginary components cancel each other out.
  • FIG. 1 8 Shown in FIG. 1 8 are three curves. An ideal capacitor curve is shown which is very similar to the response of a feedthrough capacitor, such as shown in FIG. 3. One can see that the attenuation goes up fairly linearly with frequency all the way up to very high frequencies even above 10,000 MHz. The MLCC curve is for the capacitor of FIG. 1 3.
  • the MLCC curve tracks very closely to an ideal or a feedthrough capacitor.
  • SRF self-resonant frequency
  • its attenuation tends to go up dramatically. This is because when one refers back to FIG. 1 6, the inductive and capacitive reactance elements are tending to cancel each other out.
  • the MLCC chip would look like a short circuit, in which ideal case its attenuation would be infinite. This means that if it wasn't for these resistive losses, we would have infinite attenuation at the SRF. Instead what we have is a peak of approximately 60 dB as shown. Above resonance, the MLCC capacitor becomes increasingly inductive and the attenuation drops dramatically. This is an undesirable effect and this is why feedthrough capacitors have generally been the preferred choice for use in EMI broadband filters.
  • FIGURE 1 9 shows three different size MLCC capacitors Ci - C 3 connected around a unipolar feedthrough pin or lead wire 1 14. Self-resonant frequency is dependent upon the internal inductance of a capacitor. This was illustrated and described in connection with FIG. 1 6.
  • MLCC capacitors C1-C3 would have three different resonant frequencies. This is more thoroughly described in U.S. Patent 5,973,907 and U.S. Patent 5,959,336 the contents of which are incorporated herein by reference.
  • Figure 20 is the schematic diagram for the three MLCC capacitors of FIG. 1 9.
  • FIGURE 21 shows the attenuation response for the three chip capacitor unipolar hermetic terminal in FIG. 1 9. These three capacitors Ci - C3 are acting in parallel as shown in the schematic diagram of FIGURE 20. Referring to FIG. 21 , we can see that there are now three resonant peaks representing the self-resonant frequency of each of these individual MLCC capacitors acting together in parallel. Shown for reference is the ideal capacitor response curve previously shown in FIG. 1 8. The SRF for Ci , C2 and C3 are also shown. The physically largest capacitor Ci will have the lowest self-resonant frequency whereas the physically smaller capacitor (C3) will have the highest self-resonant frequency. This is because, in general, the smaller the MLCC capacitor, the lower its internal inductance.
  • FIGURE 22 shows a different method of mounting MLCC capacitors, for example, those previously shown in FIG. 1 9.
  • this is known as the tombstone mounting position, which is a highly undesirable thing to do when the capacitor is to be used as an EMI filter or an RF decoupling device (bad mounting and bad form factor).
  • the capacitor's inductive loop area Li tends to increase.
  • the increased inductive loop area (integral of area bounded under the loop) has the effect of directly raising the inductance L as previously described in connection with FIG. 1 6. The reason this is undesirable is this particular capacitor will tend to self-resonate at a much lower frequency (and thereby becomes a less effective high frequency device or EMI filter).
  • FIGURE 23 illustrates a more desirable way to mount the MLCC capacitor 1 42 of FIG. 22.
  • This is a conventional flat surface mount technique, which has a much lower inductive loop area L2 as shown (area bounded under the loop). Accordingly, even though the two capacitors are identical in size and capacitance value, the MLCC capacitor 1 42 as shown in FIG. 23 will resonate at a much higher frequency before it starts to become undesirably inductive.
  • FIGURE 24 is known in the art as a reverse geometry MLCC capacitor 1 42'. For comparative purposes, the physical size of the MLCC capacitor illustrated in FIG. 24 is exactly the same dimensions as the MLCC capacitors 142 previously shown in FIGS. 22 and 23.
  • the important thing is the location of the termination surfaces 146' and 148'.
  • the MLCC capacitor 1 42' in FIG. 24 has been terminated along its long sides. Accordingly, its inductive loop area or the area bounded underneath the loop L3 is the smallest of all the loop configurations.
  • the capacitor 142' of FIG. 24 will self-resonate at a much higher frequency as compared to the MLCC capacitors 1 42 shown in FIGS. 22 and 23.
  • a good treatment of this is found in a technical paper entitled, A CAPACITOR'S INDUCTANCE, which was given at the Capacitor and Resistor Technology Symposium in Lisbon, Portugal, October 1 9-22, 1 999. This paper was co-authored by Robert Stevenson and Dr. Gary Ewell of Aerospace Corporation.
  • FIGURE 25 is the same electrical schematic diagram as previously illustrated in FIG. 1 6, but additionally showing the equivalent circuit model for an MLCC.
  • resistors IR and ESR are resistors IR and ESR.
  • IR is the insulation resistance of the capacitor C.
  • ESR capacitor series resistance
  • ESR capacitor series resistance
  • FIGURE 26 is a prior art chip transient suppression diode 1 54, such as a Transorb tm or the like.
  • FIGURE 27 is a schematic diagram showing the diode chip 1 54 of FIG. 26 connected between an active medical device lead wire 1 1 4 and circuit ground.
  • the dashed line shown in FIG. 27 illustrates the shielded housing of the AIMD.
  • the reason for diode chip 1 54 is to help protect the sensitive electronic circuits of the AIMD from external high voltage insults. These could be electrostatic discharges or the application to the patient of automatic (high voltage) external defibrillation (AED).
  • AEDs are commonly now found in government buildings, airports, airplanes and the like. It is very important that a pacemaker not be burned out during the application of an AED external defibrillation event.
  • 26 and 27 basically is typically an avalanche type diode which is also known in the art as a zener diode. In other words, they do not forward bias or short out until a certain voltage threshold is reached. These are also known in the art as TransorbsTM and also have other market names. Such diodes can be back to back and placed in parallel in order to suppress biphasic high voltage AED defibrillation pulses.
  • FIGURE 28 is a prior art inductor chip 1 56. There are many manufacturers of these. These can either have ferrite elements or be non- ferromagnetic. They come in a variety of size's inductance values and voltage ratings.
  • FIGURE 29 is a schematic diagram of the inductor chip 1 56 of FIG. 28.
  • an inductor circuit trace 1 58 is printed or deposited right on top of a prior art MLCC capacitor 1 42 to form an MLCC-T 1 60.
  • the advantage here is that low cost MLCCs which have been produced from very high volume commercial capacitor operations could be utilized and the inductor trace 1 58 could be printed on as a supplemental operation.
  • This forms a parallel inductor (L) - capacitor (C) resonant L-C circuit which creates a very high impedance at its resonant frequency. This is effective for suppressing a single RF frequency, such as that from magnetic Resonance Imaging (MRI) equipment, or the like.
  • MRI magnetic Resonance Imaging
  • FIGURE 31 shows yet another way to deposit an inductor shape 1 58 onto a separate substrate 1 62 to form a parallel L-C resonant circuit.
  • the substrate 1 62 could be of alumina ceramic or other suitable circuit board material. This could then be bonded with a thin adhesive layer 1 64 to a prior art MLCC capacitor 1 42.
  • the composite MLCC-T structure 1 60', including corresponding metallization surfaces 146 and 1 48 on opposite ends, is illustrated in the electrical schematic diagram of FIGURE 34 where it is evident that the structure forms a parallel L and C "tank" or bandstop circuit.
  • FIGURE 32 is an isometric view of a novel composite monolithic ceramic capacitor-parallel resonant tank (MLCC-T) 1 60" which forms a bandstop or tank filter 1 66 in accordance with previously referenced U.S. Patent Application Serial Number 1 1 /558349. Viewed externally, one can see no difference between the MLCC-T 1 60" of the present invention and prior art MLCC capacitor 142 as shown in FIG. 1 3. However, the novel MLCC-T 1 60" has an embedded inductor 1 62 which is connected in parallel across the capacitor between its opposite termination surfaces 1 46 and 148.
  • MLCC-T monolithic ceramic capacitor-parallel resonant tank
  • FIGURE 33 illustrates an exploded view of the various layers of the novel MLCC-T tank filter 1 60" shown in FIG. 32.
  • the novel MLCC tank (MLCC- T) 1 60" includes an embedded inductor 1 62.
  • the embedded inductor 1 62 shorts out the capacitor from one end to the other.
  • this forms a parallel tank circuit 1 66 which is again better understood by referring to the schematic diagram in FIGURE 34.
  • FIG. 33 one can see that as the capacitor stacks up from the top, we have an area of blank cover sheets 1 68 followed by one or more embedded inductor layers 1 62.
  • inductor traces can have a variety of shapes as further illustrated in FIGURE 83 of U.S. Patent Application Publication No. US 2007-01 1 2398 Al . It will be obvious to those skilled in the art that there are a variety of optional shapes that could also be used. Then there are a number of other blank interleafs 1 70 before one gets to the capacitor electrode plate sets, 1 50 and 1 52. One can see the capacitor electrode plate set 1 50 which connects to the left hand termination 146 and one can also see the capacitor electrode plate set 1 52 which connects to the right hand termination 1 48. In FIG. 33, only single electrodes are shown as 1 50, 1 52.
  • bottom blank cover sheets 1 68 are added to provide insulative and mechanical strength to the overall TANK filter MLCC-T 1 60".
  • solderable termination surfaces 146 and 1 48 can be a thick film ink, such as palladium silver, glass frit, a gold plating, or the like and applied in many processes that are known in the art.
  • the overall MLCC-T 1 60 which is illustrated in FIG. 32, looks identical to a prior art MLCC 1 42 as shown in FIG. 1 3.
  • a novel parallel inductor structure 1 62 creating a novel parallel tank or bandstop filter 1 66 shown in the schematic diagram of FIG. 34.
  • FIG. 35 In FIG. 35 only one pole of a quadpolar feedthrough capacitor 1 32 is shown, which is better understood by referring to its schematic diagram shown in FIG. 36.
  • a feedthrough capacitor 1 1 0 which is also known as a broadband EMI filter shown as Ci , C2, C3 and C 4 in FIG. 36.
  • a parallel resonant bandstop filter MLCC-T 1 60 In line with each one of these circuits is a parallel resonant bandstop filter MLCC-T 1 60 to block MRI pulsed RF frequencies or frequencies from similar powerful emitters.
  • the function of these bandstop filters is better understood by referring to the complete description in U.S. Patent No. 7,363,090, the contents of which are incorporated herein.
  • FIGURE 37 is a different type of prior art MLCC feedthrough capacitor 1 42 that is built into a special configuration. It is known in the art by some as a flat-through capacitor (it also has other trade names). It will be referred to herein as a flat-through capacitor 1 74. At low frequencies, the flat- through capacitor 1 74 exhibits ideal capacitance behavior versus frequency. That is, its attenuation curve versus frequency is nearly ideal. This is because it is truly a three-terminal device which acts as a transmission line in a manner similar to those of prior art discoidal feedthrough capacitors 1 1 0.
  • FIG. 38 Shown is a through or active electrode plate 1 76 that is sandwiched between two ground electrode plates 1 78.
  • the through or active electrode plate 1 75 is connected at both ends by termination surfaces 1 80 and 1 82.
  • termination surfaces 1 80 and 1 82 When the capacitor is mounted between circuit trace lands 1 84 and 1 86 as shown in FIG. 37, this connects the circuit trace together between points 1 84 and 1 86.
  • the flat-through capacitor 1 74 is also a three-terminal capacitor as illustrated in FIG. 37.
  • the point of current input /l is terminal 1
  • the point of circuit current egress / ⁇ ' is known as terminal 2
  • ground is known as terminal 3.
  • any RF currents that are flowing down the circuit trace must pass through the electrodes 1 75 of the capacitor 1 74.
  • FIGURE 39 is the schematic diagram of the prior art flat-through capacitor 1 74 as illustrated in FIG. 37. Note that its schematic diagram is the same as that for the feedthrough capacitor 1 1 0 shown in FIGS. 2 and 3. The difference is that feedthrough capacitors are inherently configured to be mounted as an integral part of an overall shield which precludes the problem of RF coupling (see FIGS. 5-7).
  • FIGURE 40 illustrates the attenuation versus frequency response curve which is shown generically for the flat-through capacitor of FIG. 37. If it wasn't for cross-coupling of RF energy, it would perform as an ideal or nearly perfect capacitor would. However, because of this cross-coupling, there is always going to be a certain frequency at which the attenuation starts to parasitically drop off as shown. This drop off is very undesirable in active implantable medical device (AIMD) applications in that there would be less protection against high frequency EMI emitters such as cellular phones and the like.
  • AIMD active implantable medical device
  • a primary object of the present invention is to provide a novel shielded three-terminal flat-through EMI/energy dissipating filter which embodies one or more flat-through capacitors whose internal electrodes are high frequency shielded, are much thicker (compared to prior art MLCC flat- through thick film electrode technology) and higher in both cross-sectional and surface area (robust and able to carry much higher through circuit currents), whose electrodes can be configured with integral co-planar inductor elements, and can be optionally configured to accept a variety of surface mounted electronic components (like additional discrete or embedded capacitors, inductors, diodes, RFID chips, and the like).
  • the higher surface area of the novel shielded three-terminal flat-through EMI/energy dissipating filter of the present invention maximizes the value of the flat-through capacitance.
  • the present invention resides in a shielded three-terminal flat-through EMI/energy dissipating filter which comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, and a plurality of shield plates substantially enveloping the active electrode plate, wherein the shield plates are conductively coupled to a grounded third terminal.
  • the plurality of shield plates include a first shield plate on a first side of the active electrode plate, and a second shield plate on a second side of the active electrode plate opposite the first shield plate.
  • the active electrode plate is insulated from the shield plates by a dielectric material such that the active electrode plate and the shield plates cooperatively form a flat-through capacitor.
  • a lead wire typically extends through at least one of the shield plates in non-conductive relation.
  • the lead wire is conductively coupled to the active electrode plate to form the first terminal.
  • a shielded fixture may be provided through which the lead wire extends in non- conductive relation.
  • the fixture may comprise an hermetic seal for, for example, an active implantable medical device (AIMP).
  • AIMP active implantable medical device
  • a plurality of active electrode plates are provide which each have a first shield plate on a first side thereof and a second shield plate on a second side thereof opposite the first shield plate.
  • Each active electrode plate is insulated from its adjacent shield plates by a dielectric material such that each active electrode plate and its adjacent shield plates cooperatively form a flat-through capacitor.
  • the shield plates are conductively coupled to a common ground.
  • a plurality of lead wires are provided which each extends through at least one of the shield plates in non-conductive relation. Each lead wire is conductively coupled to a respective active electrode plate to form the first terminal for said active electrode plate.
  • the shielded three-terminal flat-through EMI/energy dissipating filter may further include an adjacent feedthrough capacitor through which the lead wire extends prior to conductively coupling to the active electrode plate to form the first terminal.
  • a conductive pad may be conductively coupled to the active electrode plate to form the second terminal.
  • the conductive pad may comprise a wire bond pad disposed on an exterior surface of a body of dielectric material through which the active electrode plate extends.
  • the shielded three-terminal flat-through EMI/energy dissipating filter may include a plurality of co-planar active electrode plates insulated from the shield plates by a dielectric material such that each active electrode plate and the shield plates cooperatively form a flat-through capacitor. Moreover, at least one of the co-planar active electrode plates may comprise an inductor. In several illustrated embodiments, a co-planar third shield plate extends between the co-planar active electrode plates.
  • a lead wire or pin extends through at least one of the shield plates in non-conductive relation, wherein the lead wire or pin conductively couples to the active electrode plate to form the second terminal.
  • a monolithic chip capacitor (MLCC) may be conductively coupled between the active electrode plate and at least one of the grounded shield plates.
  • MLCC monolithic chip capacitor
  • a third shield plate may be disposed generally co-planarly with the active electrode plate, wherein the third shield plate is conductively coupled to the grounded third terminal. The third shield plate may substantially surround the active electrode plate and be disposed between the first and second shield plates.
  • the shielded three-terminal flat-through EMI/energy dissipating filter may further be modified such that at least a portion of the active electrode plate comprises an inductor.
  • the inductor may comprise a spiral circuit trace.
  • at least one via hole is provided for conductively coupling the shield plates to one another.
  • the via holes may be disposed about the periphery of the active electrode plate to enhance its shielding characteristics.
  • the active electrode plate may be configured to form at least a component of an "L", “ ⁇ ", “T”, “LL”, "5 element” or an "n” element passive electronic low pass filter.
  • the active electrode plate may be configured to form at least a component of a band stop filter, a diode array, or an RFID chip.
  • the shielded three-terminal flat-through EMI/energy dissipating filter utilizes passive electronic device components which are optimized for use at MRI frequencies.
  • the active electrode plate and the first and second shield plates are disposed generally perpendicularly to a lead wire conductively coupled to the active electrode plate to form the first terminal. In another embodiment, the active electrode plate and the first and second shield plates are disposed generally parallel to a lead wire conductively coupled to the active electrode plate to form the first terminal.
  • the active electrode plate and the shield plates are typically at least partially disposed within a hybrid flat-through substrate. This hybrid flat- through substrate may include surface metallization forming the third terminal.
  • the hybrid flat-through substrate is disposed adjacent to a hermetic seal for an implantable medical device such that the surface metallization is conductively coupled to a housing for the implantable medical device through a conductive ferrule of the hermetic seal.
  • the hybrid flat-through substrate may comprise a flex cable section, a rigid section, or a composite of both types.
  • the flex cable section may comprise a polyimide, Kapton or acrylic material.
  • the rigid section may comprise a high dielectric constant ceramic, alumina, fiberglass or FR4 material.
  • the rigid section of the hybrid substrate may include at least one passive electronic component conductively coupled to the active electrode plate.
  • the passive electronic component may comprise an RFID chip, a capacitor, an inductor, a band stop filter, an L-C trap filter, a diode, or a diode array.
  • the capacitor typically comprises a monolithic chip capacitor
  • the inductor typically comprises a monolithic chip inductor or a toroidal inductor.
  • the second terminal of the active electrode plate may be conductively coupled to a circuit board for an electronic device, such as the internal circuit board of an AIMD.
  • the hybrid flat-through substrate comprises a dielectric material with the active electrode plate embedded therein.
  • the active electrode plate is conductively coupled to surface metallization for at least one via hole through the substrate.
  • the shield plates comprise surface metallization applied to exterior surfaces of the hybrid flat- through substrate.
  • a conductive cap may be provided which is configured to capture the hybrid flat-through substrate and conductively couple the shield plates to a ground.
  • Such structure may be utilized in connection with a hermetic seal for an implantable medical device.
  • the hermetic seal would typically include a conductive ferrule to which the conductive cap is conductively attached, at least one lead wire extending through the ferrule in non-conductive relation and conductively coupled to the surface metallization of the via hole
  • the shielded three-terminal flat-through EMI/energy dissipating filter may be constructed such that all external components thereof comprise biocompatible materials designed for direct body fluid exposure.
  • the aforementioned RFID chips may include a wake-up feature for initializing AIMD RF telemetry circuits.
  • the aforementioned shielded three-terminal flat-through EMI/energy dissipating filters may be incorporated into a passive component network for an implantable lead of an active implantable device (AIMD).
  • the passive component network comprises at least one lead wire having a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at a distal end, an energy dissipative surface disposed adjacent to tissue or within the blood or lymph flow of a patient at a point distant from the electrode, and a diversion circuit associated with the lead wire, for selectively diverting high-frequency energy away from the electrode to said energy dissipative surface for dissipation of said high frequency energy as heat.
  • the passive component network may include an impeding circuit associated with the diversion circuit for raising the high frequency impedance of the lead wire.
  • the impeding circuit is typically disposed between said diversion circuit and the distal end of said at least one lead wire, and typically comprises an inductor or a band stop filter.
  • the at least one lead wire may comprise a portion of a probe or a catheter.
  • the energy dissipative surface may comprise a sheath, an insulative body, or a thermally conductive element.
  • the at least one lead wire may comprise at least a pair of lead wires each having a length extending between and to a proximal end and a tissue stimulating or biological-sensing electrode at a distal end.
  • the diversion circuit couples each of said lead wires to said energy dissipative surface.
  • the diversion circuit may further be coupled between the pair of lead wires.
  • the high frequency energy typically comprises an RF post frequency of a magnetic resonance scanner in a preferred embodiment.
  • the high frequency energy may further comprise a range of selected RF pulsed frequencies.
  • the diversion circuit may comprise a low pass filter including at least one of a C filter, and L filter, a T filter, a Pl ( ⁇ ) filter, an LL filter, a 5- element filter, or an "n" element filter.
  • the diversion circuit may further comprise at least one series resonant L-C trap filter.
  • the impeding circuit may include a non-linear circuit element.
  • the non-linear circuit element may comprise a diode or a transient voltage suppressor.
  • the diversion circuit may comprise at least one series resonant L-C trap filter, and wherein the impeding circuit comprises an inductor or a band stop filter.
  • the basic point of novelty of the three- terminal flat-through EMI/energy dissipating filter is that it comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, a first shield plate on a first side of the active electrode plate, and second shield plate on a second side of the active electrode plate opposite the first shield plate, wherein the first and second shield plates are conductively coupled to a grounded third terminal.
  • the effective capacitance area or overlapping surface area of the active electrode plate and its surrounding grounded shield plates have been relatively maximized in order to achieve a higher value of capacitance of the three-terminal flat-through capacitor.
  • the dielectric constant of the insulating layers between the active electrode plate and the surrounding ground shied plates have also been substantially raised in order to achieve a higher capacitance value for the three- terminal flat-through capacitor.
  • the dielectric thickness separating the active electrode plate and the surrounding ground shield plate is relatively minimized in order to achieve a higher capacitance value.
  • a number of redundant parallel layers of the active electrode plate and surrounding grounded shield plates are provided to increase the total capacitance value of the three-terminal flat-through capacitor.
  • FIGURE 1 is a wire formed diagram of a generic human body showing a number of implanted medical devices.
  • FIGURE 2 is a fragmented perspective view of a prior art unipolar discoidal feedthrough capacitor.
  • FIGURE 3 is a sectional view of the feedthrough capacitor of FIG. 2 shown mounted to a hermetic seal of an active implantable medical device
  • FIGURE 4 is a schematic diagram showing the feedthrough capacitor shown in FIGS. 2 and 3.
  • FIGURE 5 is a perspective view of a quadpolar feedthrough capacitor.
  • FIGURE 6 is sectional view taken along the line 6-6 of FIG. 5.
  • FIGURE 7 is an electrical schematic diagram of the quadpolar feedthrough capacitor of FIGS. 5 and 6.
  • FIGURE 8 is an exploded electrode view showing the inner and outer diameter electrodes of the unipolar feedthrough capacitor of FIGS. 2 and
  • FIGURE 9 is an exploded view of the interior electrodes of the quadpolar feedthrough capacitor show in FIG. 5.
  • FIGURE 10 is a perspective view of a quadpolar feedthrough capacitor mounted on top of a hermetic seal.
  • FIGURE 1 1 is a sectional view taken generally along the line 1 1 -1 1 of FIG. 10.
  • FIGURE 1 2 is an electrical schematic diagram of the quadpolar hermetic feedthrough terminal shown in FIG. 10.
  • FIGURE 1 3 is a perspective view of a monolithic ceramic capacitor
  • FIGURE 14 is a sectional view taken generally along the line 14-1 4 of FIG. 1 3.
  • FIGURE 1 5 is an electrical schematic diagram of an ideal MLCC capacitor as illustrated in FIG. 1 3.
  • FIGURE 1 6 is a more realistic electric schematic diagram of the
  • FIGURE 1 7 is a chart giving the formula for resonance frequency.
  • FIGURE 1 8 is a graph showing filter attenuation versus frequency.
  • FIGURE 1 9 is a perspective view of a unipolar terminal having three different size MLCC capacitors connected to the feedthrough pin.
  • FIGURE 20 is an electrical schematic diagram of the structure shown in FIG. 1 9.
  • FIGURE 21 is a graph showing the attenuation response for the three chip capacitor unipolar hermetic terminal shown in FIG. 1 9.
  • FIGURE 22 illustrates a different method of mounting the MLCC capacitors such as those shown in FIG. 1 9.
  • FIGURE 23 illustrates a more desirable way to mount the capacitor of FIG. 22.
  • FIGURE 24 shows yet another way of mounting the MLCC capacitor of FIGS. 22 and 23.
  • FIGURE 25 is an electrical schematic diagram showing an equivalent circuit model for the MLCC chip capacitor.
  • FIGURE 26 is a perspective and schematic view of a prior art MLCC transient suppressant diode.
  • FIGURE 27 is an electrical schematic diagram of the diode of FIG.
  • FIGURE 28 is a perspective and schematic diagram of a prior art chip inductor.
  • FIGURE 29 is an electrical schematic diagram of the inductor chip of
  • FIG. 28. [Para 96] FIGURE 30 is a perspective view of an MLCC capacitor having an inductor circuit trace deposited thereon.
  • FIGURE 31 is an exploded perspective view of a structure similar to FIG. 30 showing another way to deposit the inductor shape onto a separate substrate.
  • FIGURE 32 is a perspective view of a composite monolithic ceramic capacitor-parallel resonant tank (MLCC-T) or bandstop filter.
  • FIGURE 33 is an exploded perspective view of the various layers of the MLCC-T tank filter of FIG. 32.
  • FIGURE 34 is an electrical schematic diagram of the MLCC-T tank or bandstop filter of FIGS. 32 and 33.
  • FIGURE 35 is a sectional view of one pole of a quadpolar feedthrough capacitor embodying an MLCC-T filter.
  • FIGURE 36 is an electrical schematic diagram of the quadpolar device partially shown in FIG. 35.
  • FIGURE 37 is a perspective view of a prior art flat-through capacitor.
  • FIGURE 38 is a diagram showing the internal electrode array of the flat-through capacitor of FIG. 37.
  • FIGURE 39 is an electrical schematic diagram of the prior art flat- through capacitor of FIGS. 37 and 38.
  • FIGURE 40 illustrates the attenuation versus frequency response curve of the typical flat-through capacitor of FIGS. 37 and 38.
  • FIGURE 41 is a perspective view of a quadpolar EMI filter hermetic seal similar to that shown in FIG. 10, but embodying a shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • FIGURE 42 is a sectional view taken generally along the line 42-42 of FIG. 41 .
  • FIGURE 43 is a sectional view taken generally along the line 43-43 of FIG. 41 .
  • FIGURE 44 is a sectional view taken generally along the line 44-44 of FIG. 41 .
  • FIGURE 45 is a sectional view taken generally along the line 45-45 of FIG. 41 .
  • FIGURE 46 is a sectional view taken generally along the line 46-46 of FIG. 41 .
  • FIGURE 47 is an exploded perspective view of the plates forming the flat-through EMI/energy dissipating filter of FIGS. 41 -46.
  • FIGURE 48 is a sectional view taken generally along the line 48-48 of FIG. 41 .
  • FIGURE 49 is an electrical schematic drawing of the flat-through
  • FIGURE 50 is a sectional view similar to FIGS. 43 and 44 illustrating incorporation of stacked layers Li and l_2 into a single co-planar layer.
  • FIGURE 51 is a sectional view similar to FIGS. 42-46, showing modification of the active electrode plates for connection to a via hole.
  • FIGURE 52 is a fragmented perspective view illustrating a lead wire extending into one of the via holes of FIG. 51 .
  • FIGURE 53 is a view similar to FIG. 52, showing an alternative bond pad in place of the wire.
  • FIGURE 54 is a perspective view of a unipolar hermetic seal similar to that shown in FIG. 3, except that it is inverted with the feedthrough capacitor replaced with a shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • FIGURE 55 is a fragmented view of the area indicated by line 55-55 in FIG. 54, illustrating an alternative way of attaching a lead wire.
  • FIGURE 56 is a sectional view taken generally along the line 56-56 of FIG. 54.
  • FIGURE 57 is a fragmented sectional view showing an alternative connection methodology wherein a via hole is filled and then attached to a solder bump.
  • FIGURE 58 is an exploded perspective view of various components forming the structure of FIGS. 54 and 56.
  • FIGURE 59 is an electrical schematic for the structure of FIGS. 54,
  • FIGURE 60 is a perspective view showing modification of an active electrode plate layer shown in FIG. 58.
  • FIGURE 61 is a view similar to FIG. 60, wherein the active electrode plate has been modified by adding a spiral inductor element.
  • FIGURE 62 is an electrical schematic for the inductor-capacitor filter formed by the substrate of FIG. 61 .
  • FIGURE 63 is an exploded perspective view of a quadpolar filter assembly incorporating a shielded three-terminal flat-through EMI/energy dissipating filter in accordance with the present invention.
  • FIGURE 64 is a top plan view showing a modification of the grounded shield plates of FIG. 63.
  • FIGURE 65 is a view similar to FIG. 64 of the grounded shield plates, showing additional modifications.
  • FIGURE 66 is similar to FIGS. 64 and 65, showing an alternative configuration of the grounded shield plates.
  • FIGURE 67 is a perspective view of an alternative arrangement of the active electrode plate substrate of FIG. 63.
  • FIGURE 68 is a graph illustrating attenuation versus frequency comparing the performance of the shielded three-terminal flat-through EMI/energy dissipating filter of FIGS. 63 with other technologies.
  • FIGURE 69 is an exploded isometric view that is similar to FIG. 63 wherein the active electrodes have been modified to include inductors.
  • FIGURE 70 is an exploded view very similar to FIGS. 63 and 69 except that edge shields and optional separating shields have been placed to prevent EMI radiation from the active electrode plates or optionally between co- planar electrode plates.
  • FIGURE 71 is an exploded perspective view of an alternative form of the shielded three-terminal flat-through EMI/energy dissipating filter similar to
  • FIG. 63 is a diagrammatic representation of FIG. 63.
  • FIGURE 72 is an enlarged view of a round Wheeler spiral shown forming a portion of an active electrode plate in FIG. 69.
  • FIGURE 73 is similar to FIG. 72, showing a square Wheeler spiral such as those shown forming portions of the active electrode plates in FIGS. 69,
  • FIGURE 74 illustrates several typical inductor meander shapes.
  • FIGURE 75 illustrates the attenuation curves for various types of low-pass filters.
  • FIGURE 76 is a family of filter attenuation curves similar to that shown in FIG. 68.
  • FIGURE 77 is a perspective view of a bipolar hermetically sealed filter embodying the shielded three-terminal flat-through EMI/energy dissipating filter present invention.
  • FIGURE 78 is an exploded perspective view of the internal layers of the shielded three-terminal flat-through EMI/energy dissipating filter of FIG.
  • FIGURE 79 is an exploded perspective view of an alternative embodiment embodying the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • FIGURE 80 is a partially fragmented view of the assembled section of FIG. 79 taken along the line 80-80 of FIG. 79.
  • FIGURE 81 is an electrical schematic diagram of the quadpolar shielded three-terminal flat-through EMI/energy dissipating filter shown in
  • FIGS. 79 and 80 are identical to FIGS. 79 and 80.
  • FIGURE 82 is an exploded perspective view of an inline hybrid substrate embodying the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • FIGURE 83 is an electrical schematic diagram of the structure shown in FIG. 82.
  • FIGURE 84 is an exploded perspective view of another form of a shielded three-terminal flat-through EMI/energy dissipating filter embodying the present invention.
  • FIGURE 85 is similar to FIG. 84 except that the diode array has been replaced with an RFID chip.
  • FIGURE 86 is similar to FIG. 84, wherein toroidal inductors have been used to replace a series of surface mount chip inductors.
  • FIGURE 87 is a view similar to FIG. 84, illustrating the flexibility of a portion of a hybrid substrate.
  • FIGURE 88 is an internal diagrammatic view of the novel hybrid substrate of FIG. 84.
  • FIGURE 89 is an electrical schematic diagram of the novel hybrid substrate of FIG. 84.
  • FIGURE 90 is the same as one of the active circuits of FIG. 89 wherein the "T" circuit filter has been replaced with a ⁇ circuit filter.
  • FIGURE 91 is similar to FIG. 84, with the addition of a prior art quadpolar feedthrough capacitor.
  • FIGURE 92 is a plan view of the reverse side of the flexible portion of the hybrid substrate of FIGS. 84 and 88.
  • FIGURE 93 is a sectional view taken generally along the line 93-93 of FIG. 92.
  • FIGURES 94-97 are fragmented sectional views taken generally of the area indicated by the line 94, 95, 96 and 97 in FIG. 93, showing alternative methods of making an electrical connection.
  • FIGURE 98 is a plan view similar to FIG. 92 showing a modified version of flex cable assembly with four via holes.
  • FIGURE 99 is a cross-sectional view of the area indicated by line
  • FIG. 93 showing type of yet another embodiment illustrating attachment of the substrate over a terminal pin utilizing a weld ring or a braze ring.
  • FIGURE 100 is a view similar to FIG. 99 illustrating yet another methodology of attachment.
  • FIGURE 101 is an isometric cross-section of a novel attachment cap used to connect the shielded three-terminal flat-through EMI/energy dissipating filter to various types of hermetic or non-hermetic seals.
  • FIGURE 102 is a cross-sectional view of a prior art hermetic seal embodying the novel cap from FIG. 1 01 .
  • FIGURE 103 is a schematic view illustrating a methodology of having a circuit trace or a portion of an electrode plate dodge around a via hole.
  • FIGURE 104 is a schematic illustration of an alternative embodiment to FIG. 84.
  • FIGURE 105 is similar to FIG. 1 04, except that it illustrates the methodology of breaking up flex cable section of the hybrid substrate into flexible sections.
  • FIGURE 106 is an exploded perspective view of an in-line octapolar hermetic terminal with a shielded three-terminal flat-through EMI/energy dissipating filter hybrid flat-through substrate embodying the present invention.
  • FIGURE 107 is a flow chart illustrating a manufacturing production process.
  • FIGURE 108 is an exploded perspective view of a typical sixteen lead hermetic seal utilizing a novel hybrid shielded three-terminal flat-through
  • FIGURE 109 is an electrical schematic diagram of the structure of
  • FIG. 108
  • FIGURE 1 1 0 is a perspective view of a five pin terminal.
  • FIGURE 1 1 1 is a perspective view of the five pin terminal of FIG.
  • FIGURE 1 1 2 is a perspective view similar to FIG. I l l , showing an alternative embodiment wherein reversed geometry MLCC's are utilized to provide high frequency attenuation.
  • FIGURE 1 1 3 is a flow chart illustrating an exemplary manufacturing process of the electronic components of the present invention.
  • FIGURE 1 1 4 is an illustration of an exemplary AIMD showing the use of variable impedance elements in connection with a lead wire within the housing of the AIMD.
  • FIGURE 1 1 5 is a schematic illustration of the structure shown in
  • FIG. 1 1 showing use of variable impedance elements on leads that ingress and egress the AIMD.
  • FIGURE 1 1 6 is a schematic illustration showing that a variable impedance element can be a capacitor element.
  • FIGURE 1 1 7 is a schematic illustration similar to FIG. 1 1 6, showing that the variable impedance element can be a feedthrough capacitor element.
  • FIGURE 1 1 8 is a schematic illustration similar to FIGS. 1 1 6 and 1 1 7, showing that the variable impedance element can be an L-C trap filter.
  • FIGURE 1 1 9 is a schematic illustration similar to FIG. 1 1 8, showing use of a capacitor element in parallel with the L-C trap filter.
  • FIGURE 1 20 is similar to FIG. 1 1 5 with emphasis on the series variable impedance element.
  • FIGURE 1 21 illustrates that the variable impedance element can be an inductor.
  • variable impedance element can be an L-C bandstop filter.
  • FIGURE 1 23 is an attenuation versus frequency chart showing impedance characteristics of various types of filters.
  • FIGURE 1 24 is a schematic diagram of a series inductor-capacitor filter commonly known in the industry as an L-C trap filter.
  • FIGURE 1 25 is a chart giving the resonant frequency equation for an L-C series trap filter.
  • FIGURE 1 26 illustrates the impedance Z in ohms versus frequency of the series resonant L-C trap filter of FIG. 1 24.
  • FIGURE 1 27 is similar to the chart similar to FIG. 1 26, illustrating the impedance in ohms versus frequency of two discrete series resonant L-C trap filters.
  • FIGURE 1 28 is an overall outline drawing showing a cardiac pacemaker with endocardial lead wires implanted into a human heart.
  • FIGURE 1 29 is a cross-sectional view of a human head showing a deep brain stimulator electrode.
  • FIGURE 1 30 is a schematic illustration of a unipolar lead system for an AIMD.
  • FIGURE 1 31 is an illustration similar to FIG. 1 30, including an L-C trap filter.
  • FIGURE 1 32 is another illustration similar to FIG. 1 30, wherein the frequency selective components comprise capacitive elements.
  • FIGURE 1 33 is another illustration similar to FIGS. 1 30 and 1 32, wherein the capacitance value C has been selected such that the capacitive reactance will be equal and opposite to the inductive reactance of the implanted lead.
  • FIGURE 1 34 illustrates prior art hermetic and non-hermetic connectors that are typically used in the military, aerospace, medical, telecommunication and other industries.
  • FIGURES 1 35 and 1 36 illustrate a prior art sub D-type connector.
  • FIGURE 1 37 and 1 38 show prior art hermetic connectors.
  • FIGURE 1 39 shows an exploded view of a prior art multi-pin connector and a shielded three-terminal flat-through EMI filter.
  • FIGURE 140 is similar to FIG. 1 39 except that the shielded three- terminal flat-through EMI filter of the present invention has been attached.
  • FIGURE 141 is an exploded view taken generally from section 1 41 - 1 41 of FIG. 1 39 showing a surface mounted MLCC capacitor.
  • the present invention is concerned with shielded three-terminal flat-through EMI/energy dissipating filters 1 90 which can be embodied in substrates or flex cable assemblies.
  • the novel concept resides in designing an embedded flat-through capacitor wherein optional surface mounted passive or active components can be attached while at the same time providing an interconnection circuit.
  • the novel shielded three-terminal flat-through EMI/energy dissipating filters 1 90 embody a flat-through capacitor that has similar characteristics to prior art feedthrough EMI filter capacitors.
  • the flat-through EMI/energy dissipating filter 1 90 of the present invention provides three-terminal capacitive filtering while simultaneously providing shielding of circuits and signals passing through the robust high current capability electrodes of the flat-through capacitor.
  • the flat-through EMI/energy dissipating filter 1 90 of the present invention functions in a very equivalent manner to prior art feedthrough capacitors in that: a) its internal ground plates act as a continuous part of the overall electromagnetic shield housing of the electronic device or module which physically blocks direct entry of high frequency RF energy through the hermetic seal or equivalent opening for lead wire ingress and egress in the otherwise completely shielded housing (such RF energy, if it does penetrate inside the shielded housing can couple to and interfere with sensitive electronic circuitry); and, b) like prior art feedthrough capacitors, the flat-through EMI/energy dissipating filter 1 90 of the present invention very effectively shunts undesired high frequency EMI signals off of the lead wire (electrodes) to the overall shield housing where such energy is
  • the circuit currents for example pacemaker pacing pulses or ICD HV defibrillation high current shocks
  • the circuit currents must pass through the internal electrodes of the embedded flat-through capacitor.
  • the flat-through electrodes can be manufactured with much thicker electrodes (like copper sheet) which greatly increases their capability to safely carry relatively higher through circuit currents (like external or internal cardiac defibrillation pulses).
  • FIGURE 41 is a very similar to the quadpolar EMI filtered hermetic seal that was illustrated in FIG. 10.
  • the feedthrough capacitor element has been completely eliminated, thus significantly reducing the cost of manufacture.
  • the feedthrough capacitor 1 32 and its associated wire bond substrate 1 36 that were described in FIG. 1 0 have been replaced by a novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90.
  • wire bond pads 1 38, 1 38', 1 38", 1 38'" and 1 40 are very similar to the wire bond pads illustrated in FIG. 1 0. They are attached to a relatively higher K ceramic or suitable hybrid substrate 1 92. Novel parasitic flat-through capacitors of the present invention are integrated into the substrate 1 92. This is better understood by referring FIGURES 42 through 46.
  • FIG. 42 illustrates a grounded shield plate 1 94.
  • the center pin 1 96 is grounded. That is, there is a web plate (not shown) underneath the substrate 1 92 wherein the ground pin 1 96 is electrically coupled to the metallic ferrule 1 20 of the hermetic seal 1 1 2. It is important that this be a low inductance RF ground.
  • the web plate would be a high surface area plate with clearance holes only for the pass through of lead wires 1 1 4, 1 14', 1 14" and 1 14'".
  • This RF grounded web plate could, for example, have its outer diameter laser welded to the ferrule 1 20 of the hermetic terminal and its inside diameter hole welded or soldered to the grounded lead wire or pin 1 96.
  • FIG. 48 An alternative methodology of grounding the center pin 1 96 is illustrated with embedded ground plates within the hermetic seal as shown in FIG. 48.
  • FIG. 48 one can see that there is a hermetic insulator 1 1 8 through which the lead wires pass in non-conductive relation to the metallic ferrule 1 20. Shown are ground plates 1 98 embedded in the insulative portion 1 1 8 of the hermetic seal 1 1 2 which are attached by gold brazing to the center ground pin 1 96. Grounding this centered pin 1 96 using plates embedded in the insulator 1 1 8 of the hermetic seal 1 1 2 has been described in U.S. Patent No. 7,1 99,995, the contents of which is incorporated herein by reference. Other methods of grounding pin 1 96 are further described in U.S. Patent Nos. 5,905,627 and 6,529, 103, the contents of which are also incorporated herein by reference.
  • FIGS. 43 through 46 illustrate the internal active electrode plate layouts 1 76, 1 76', 1 76" and 1 76'".
  • the overlap area which is otherwise known as the effective capacitance area (ECA) of each of these active electrode plates has been maximized in order to maximize the flat-through capacitance.
  • Maximizing the thickness and the area of the active electrode plates 1 76-1 76'" also has an added benefit in that their overall resistance is lowered (and its current rating is greatly increased). This is important because circuit currents of the novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 must pass through the respective electrode plates 1 76-1 76'" in order to accomplish the novel shielded flat-through capacitor characteristics.
  • novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention overcomes both of the foregoing negatives associated with prior art flat-through capacitors by incorporating grounded shield plates 1 94 surrounding on at least the top and bottom sides a novel high surface area and relatively thick flat-through active electrode plate 1 76 through which circuits of up to 30-amps or greater can pass.
  • the novel high surface area electrodes 1 76 of the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 can optionally include inductor sections which not only desirably add series inductance to the filter but also increase the flat-through capacitance by increasing the effective capacitance area (ECA).
  • ECA effective capacitance area
  • EMI or RF will undesirably cross-couple across the prior art flat-through capacitor 1 74 or, potentially worse yet, couple to adjacent circuits.
  • the flat-through capacitance is very well shielded. In this case, the flat-through capacitance will act as an ideal capacitor and will be free of resonances and parasitic RF coupling degradation.
  • an optional external metallization 1 08 that is connected to the interior grounded shield electrode plates 1 94.
  • the external metallization 1 08 would be directly electrically connected to gold braze 1 24 (in this case, the diameter of the ferrule 1 20 would need to be enlarged. Accordingly, the RF grounding and impedance would be lowered between the ferrule 1 20 and the outer metallization 1 08 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90. In this case, it will be obvious that the center ground pin 1 96 could be eliminated and the internal ground electrodes 1 98 within the hermetic insulator 1 1 8 could also be eliminated.
  • the grounding of the shield electrode plates 1 94 could be accomplished either by the center pin 1 96 as shown in FIG. 48, or be done around the outside perimeter or circumference with an attachment between the external metallization 1 08 and for example, gold braze 1 24.
  • Adding metallization 1 08 means that the embedded active flat-through electrode plates 1 76 are RF shielded by top and bottom plates 1 94 and on their co-planar edges by shield 108. This means that the active electrode plates 1 76 are completely shielded such that RF re-radiation or cross coupling cannot occur.
  • Insulative washer 200 which is disposed between the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 and the hermetic insulator body 1 1 8. This is to make sure that the electrical connection materials 1 28 cannot migrate underneath the hybrid substrate 1 92 and cause shorting between adjacent pins. For example, if electrical conductive material 1 28 were to migrate between pins 1 1 4" and 1 14'" this could short out the output of a cardiac pacemaker.
  • Insulating layer 200 in a preferred embodiment is also an adhesive.
  • the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 is firmly affixed to the hermetic seal 1 1 2. This makes the subsequent electrical attachment operations by soldering, centrifuging of thermally conductive polyamides or epoxies or the like, more convenient.
  • the body fluid side is shown on the bottom side of hermetic insulator 1 1 8. It is typical that electronic circuits for AIMDs be inside the hermetic and electromagnetically shielded housing. However, the present invention is not limited to only placing the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 on the inside of the housing of the AIMD.
  • FIGURE 49 is a schematic drawing of the novel shielded three- terminal flat-through EMI/energy dissipating filter 1 90 of FIG. 41 .
  • Shields 1 94 through 1 94"" illustrate the fact that the high surface area active electrode plates 1 76 are surrounded at least on top and bottom by grounded shield electrode plates 1 94 that form the flat-through effective capacitance overlap area and at the same time prevent undesirable RF coupling across the flat- through capacitive filter.
  • the feedthrough capacitances Ci , C2, C3 and C 4 have been formed by the overlap area (ECA) between each of the active electrodes 1 76 and the corresponding shield plates 1 94 that surround the active electrodes on both top and bottom.
  • ECA overlap area
  • active electrode plate 1 76-1 76' have been surrounded on top and bottom by grounded shield plates 1 94-1 94"".
  • k is the permittivity or dielectric constant of the insulative dielectric material itself;
  • A is the effective capacitance area in in 2 or mm 2 (ECA) determined by the overlap of the grounded shield plates 1 94 and 1 94' and, for example, the active electrode 1 76;
  • n is the number of total electrode areas; and, d is the dielectric thickness.
  • insulative dielectric cover sheets (not shown) which can be the same or different insulating and/or dielectric material that forms the dielectric layer on each of the electrode layers (this is to add additional electrical and mechanical protection).
  • the first decision a designer makes is what is the required dielectric thickness for the voltage rating of the application and then adjust the ECA such that the desired flat-through capacitance is achieved. In some cases, not enough flat-through capacitance will be achieved to adequately filter all frequencies.
  • FIGURE 50 illustrates a way to produce the novel hybrid EMI filter substrate 1 92 of FIG. 41 with less layers and a correspondingly lower overall substrate thickness. This is accomplished b y incorporating two (or more) active electrode 1 76 and 1 76' onto a single co-planar layer. Putting multiple active electrode plates on co-planar layers has the desired effect of making the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 thinner, easier to manufacture and less expensive. However, this has the undesirable effect of reducing the effective capacitance area (ECA) for each active electrode plate 1 76. However, when high K materials are used, the effective capacitance area is so large that this is really not a detriment.
  • ECA effective capacitance area
  • novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 can be constructed of prior art flex circuit techniques (like polyimide flex circuits), multilayer rigid substrates (like alumina or FR 4 board), thick film deposition onto a substrate or carrier, or the like. For each of these manufacturing techniques, there is a practical limit to the number of layers that can be built up.
  • FIG. 51 shows that, for example, the active electrode plate 1 76 shown in FIG. 43 could be modified such that it was connected to a via hole 202.
  • This via hole 202 provides for a convenient connection of either a lead wire 204, as shown in FIG. 52, or a round (or rectangular, square or other not shown) wire bond pad 206 as illustrated in FIG. 53.
  • FIGURE 54 is an isometric drawing of a unipolar pacemaker hermetic seal 1 1 2 that is similar to that shown in FIG. 3 except that the feedthrough capacitor has been replaced with a shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention shown mounted on top of the insulator 1 1 8 and gold braze 1 24.
  • the hybrid substrate 1 92 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 can be manufactured from any number of the techniques previously described herein..
  • the body of the hybrid substrate 1 92 could be a conventional substrate consisting of high dielectric constant ceramic, alumina, ceramic, fiberglass, FR 4 or any other rigid type of multi-layer board technology.
  • the hybrid substrates 1 92 could be made of a number of flexible or flex cable variances. These could include flex cables that are laminated together based on polyimide, Kapton and acrylic construction. Another embodiment would be polyimide flex cables with all polyimide connections which are laminated together at high temperature. All of these types of boards and/or substrates and/or flex cables are known in the art. What is described herein is a very novel adaptation of those boards and substrates to flat-through filter technology. Hereinafter, the novel substrates incorporating various forms of novel shielded flat-through EMI filter technologies will be referred to as the hybrid substrates 1 92. [Para 21 5] In FIG. 54, one can see that there is a metalized area 208 on the hybrid substrate 1 92.
  • This wrap-around metalized area 208 makes connection to internal ground shield plates 1 94 and 1 94' embedded within the hybrid substrate 1 92 as shown in Fig 56.
  • a plurality of electrical connections 210,21 0' and 21 0 '" as shown the equivalent electrical connections 210" and 21 0"" on the opposite side of substrate 1 92 are not shown).
  • These electrical connections connect to gold braze 1 24 that is part of the hermetic seal and provides an "oxide-free" RF ground multi-point connection. This is better understood by referring to FIG. 56 which is taken from section 56-56 of FIG. 54.
  • the importance of connecting to a gold braze instead of connecting directly to the titanium ferrule 1 20 can be better understood by referring to U.S.
  • Patent Nos. 6,765,779 and 6,765,780 the contents of which are incorporated herein. From FIG. 56, one can see that there is a prior art hermetic seal 1 1 2 which includes a metal ferrule 1 20 which is typically of titanium or the like. There is a flange area 21 2 shown which is convenient for laser welding to the titanium housing of an AIMD, such as a cardiac pacemaker or the like. There is a hermetic insulator 1 1 8 which can be of alumina, ceramic materials, glass or equivalent. In this particular embodiment, there is a gold braze 1 24 which forms a mechanical and hermetic seal between the insulator 1 1 8 and the ferrule 1 20.
  • a gold braze 1 22 makes a similar mechanical and hermetic seal between the lead wire 1 1 4 and the insulator 1 1 8.
  • the body fluid side would be towards the bottom of the cross-sectional illustration of FIG. 56.
  • An electrical connection is made between lead wire 1 1 4 and the metalized via hole 202 which is part of the novel hybrid substrate 1 92.
  • the via hole 202 makes electrical connection to internal active electrode (otherwise known as the flat-through electrode) plate 1 76 as shown, which in turn is connected to via hole 202'.
  • the grounded electrode shield plates 1 94 and 1 94' are connected to the outside metallization surface 208 of the hybrid substrate 1 92.
  • this metallization 208 is electrically connected via material 210 to the gold braze 1 24 of the hermetic seal 1 1 2.
  • this direct connection to gold makes a reliable oxide free low impedance connection, the importance of which is described thoroughly in U.S. Patent Nos. 6,765,779 and 6,765,780.
  • a prior art monolithic ceramic chip capacitor (MLCC) 1 42 has been electrically connected to lands which are in turn connected to via holes 202' and 202". This is better understood by referring to the exploded view of Fig. 54 shown in FIG. 58.
  • via hole 202' is connected to the active circuit electrode 1 76.
  • the other side of the MLCC capacitor 1 42 is connected by via hole 202" to both of the grounded shield electrode plates 1 94 and 1 94'. It is important that a very low impedance connection has been made to both sides of the MLCC capacitor 1 42.
  • any type of chip capacitor could be used.
  • MLCC capacitor 1 42 need not be connected to RF ground by way of the via 202" as shown. Instead, an enlarged land on the left side of the MLCC 1 42 could be RF grounded directly to the external wrap-around metallization surfaces 208.
  • FIG. 54 shows an alternative arrangement wherein the wire bond pad 1 38 (which would typically be made of Kovar) has been eliminated. In FIG. 55, there is a different type of plated of metal deposited wire bond pad 1 39. In this case, no separate attachment of a Kovar block 1 38 is required as illustrated in FIG. 54. In this case, in FIG. 55, wire bond pad 1 39 can be an integral part of an external circuit trace and deposited by plating, thick film deposition technique and the like.
  • an electrical connection material 214 that is disposed between the lead wire 1 14 and the via hole 202.
  • This can be of a thermal setting conductive polymer, such as a conductive epoxy or a conductive polyimide or the like.
  • Material 21 4 could also be of solder or braze, which is known in the art as solder bump construction or even ball grid array (BGA). It is shown in the reflowed position so it is not obvious that this started out as a round ball.
  • one or more adhesive backed insulative washers 200 are disposed between the hermetic seal 1 1 2 and the hybrid substrate 1 92.
  • this washer 200 would be an adhesive backed polyimide or the like to make sure that electrical conductive materials such as 21 4 stay in place and could not short and/or migrate to areas where they were not desired (like a short to ground).
  • a laminar leak detection path can be provided between the washer 200 to facilitate helium leak testing of the hermetic seal.
  • a similar electrical connection material 21 0 disposed between metallization surface 208 and gold braze 1 24.
  • Material 21 0 is also typically a thermal setting conductive adhesive, solder, low temperature braze, laser weld, or the like.
  • a wire bond pad 1 38 is shown connected to the active electrode plate 1 76.
  • any electrical noise (EMI) that was entering from the body fluid side on lead wire 1 14 has been decoupled by the filtering action of the flat-through capacitances shown in FIG. 56 as Cp and Cp' and the MLCC 142 working together.
  • the flat-through capacitance is relatively lower in value than the MLCC 1 42; however, it is very effective for attenuating high frequencies. Lower frequencies are attenuated by the higher capacitance value MLCC capacitor 142.
  • Wire bond pad 1 38 is convenient for connection of one or more lead wires 204 to internal circuit components inside of the general electronic shielded module or an AIMD.
  • FIG. 56 In FIG. 56 one can see that via hole 202 is connected to lead wire 1 14 by means of an electrical conducting material 21 4 which can be solder, a low temperature braze, a thermal-setting conductive adhesive or the like.
  • An alternative methodology is shown in FIG. 57 wherein the via hole 202 is filled and then attached to a solder bump 21 6 as shown.
  • the solder bump 21 6 makes contact to the metallization 1 06 of via hole 202.
  • the solder bump 21 6 wets to the nail head lead 21 8 forming a reliable electrical and mechanical connection.
  • FIGURE 58 is an exploded view of FIG. 54.
  • a low impedance RF electrical connection to the ground shield plates 1 94 and 1 94' is very important. Accordingly, one can see that there are multiple electrical attachments 21 0 to 210"". This, of course, could be one long continuous connection all around the ground metallization 208 to the gold braze 1 24. However, it is desirable to not block a helium leak path. The integrity of these hermetic terminals is critical to preclude the entry of body fluid into the AIMD. [Para 223] Referring once again to FIG.
  • body fluid moisture
  • body fluid moisture
  • helium a leak detection medium
  • adjunct components such as the hybrid substrate 1 92 of the present invention, could temporarily block the flow of helium.
  • a helium leak test is performed in a few seconds.
  • any adjunct sealant such as a continuous coverage of conductive thermal setting adhesive 210 or the like, could slow down the flow of helium through such coverings. Accordingly, in the preferred embodiment of the present invention, it is desirable to leave open gaps as shown in FIGS. 54 and 58 between areas of electrical attachment. In this way, if there are any defects 220 in the hermetic terminal insulator 1 1 8 or its associated gold brazes 1 22 and 1 24, the helium will be free to pass and be detected by the leak test equipment. As taught by U.S. Patent No. 6,566,978, the contents of which are incorporated herein by reference, it will be obvious to those skilled in the art that strategically placed open via holes through the hybrid substrate 1 92 could be provided in order to pass helium during hermetic seal testing.
  • a novel aspect of the present invention is that flat-through capacitance develops between the circuit active electrode plate 1 76 and the surrounding grounded shield electrode plates 1 94 and 1 94'. This capacitance is shown as Cp and Cp'.
  • the novel hybrid substrate 1 92 shown in FIG. 56 could be constructed of a variety of different materials.
  • the dielectric constant of a polyimide material would be between 3 and 4 whereas an alumina ceramic material could be as high as 9 to 1 1 .
  • Barium and strontium titinate dielectric bodies can have dielectric constants in excess of 5000.
  • A stands for the area, which is the effective capacitance area (ECA). This is calculated by the sandwiched overlap between the area of circuit active electrode plate 1 76 and the corresponding ground electrode shield plates 1 94 and 1 94'. Ignoring fringe effects, a simplified way of calculating this area is simply the area of active electrode plate 1 76 that is bounded between the sandwiched grounded shields 1 94 and 1 94'.
  • r ⁇ is the total number of repetitive electrode plates.
  • the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 of the present invention acts in equivalent way to prior art feedthrough capacitors in that the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 is not only an effective filter and energy dissipation element, it's ground electrode plates 1 94 act as an effective part of the overall electromagnetic shield housing of the AIMD or other equivalent shielded electronic circuit.
  • the inductance although quite small, is relatively maximized due to the relatively long length of active electrode plate 1 76 and the fact that it is relatively narrow.
  • the flat-through (parasitic) capacitance is the sum of the parallel combination of Cp and Cp- and is relatively maximized due to the large area of the active electrode 1 76 and the high ECA achieved by its overlap with the grounded shield plates 1 94 and 1 94'.
  • One way to further increase the total amount of flat-through (parasitic) capacitance would be to increase the number of layers in FIG. 58. In a monolithic construction, repeating the number of redundant layers would increase the capacitance by the r ⁇ -l term of the capacitance equation. Additional ways to increase the amount of flat-through capacitance would be to further increase the effective capacitance overlap area ECA, increase the dielectric constant or decrease the dielectric thickness (d).
  • Prior art feedthrough capacitors make for very low inductance broadband low-pass filters. This is why they have generally been the preferred EMI filter at the point of lead wire ingress and egress for AIMDs and other devices.
  • feedthrough capacitors are generally built in low volumes in the industry. Because of this, they tend to be relatively high in price when compared to the much higher volumes MLCC capacitors. It is not unusual for a single feedthrough capacitor to cost several dollars, wherein an MLCC capacitor can cost just a few cents.
  • prior art feedthrough capacitors tend to be quite low in capacitance value (primarily in the range from 400 to 4000 picofarads).
  • feedthrough capacitors make very effective high frequency filters above 25 MHz, but off little attenuation at low frequencies (below 5 MHz).
  • Feedthrough capacitors in general, can be a hundreds of times more costly than equivalent value MLCC capacitors.
  • MLCC capacitors are marginal or insufficient for attenuating high frequency emitters that AIMD patients can be exposed to. This includes cellular telephones, RF identification (RFID), airport radars, microwave ovens and the like. As described in connection with FIG. 37, one possible solution would be to use flat-through capacitor technology.
  • the parasitic capacitance or flat-through capacitance works in parallel with the capacitance of the discrete MLCC capacitor 142 which results in a very effective broadband low-pass filter from kilohertz frequencies all the way to 1 0 gigahertz or higher.
  • Shields 1 94-1 94 n are illustrative to indicate that the entire flat-through filter is sandwiched between RF shield plates in such a way that high frequency EMI signals cannot re-radiate from the active electrode plate(s) 1 76. This is a very important concept. Until the undesirable EMI energy is decoupled to ground, it cannot be left unshielded inside the overall electromagnetically shielded housing of the electronic device or AIMD.
  • such high frequency noise could cross-couple into sensitive AIMD sense circuits. For example, if a cardiac pacemaker senses such high frequency noise as a heartbeat, the pacemaker could inhibit which could be life-threatening for a pacemaker-dependent patient.
  • FIGURE 60 illustrates an alternative active electrode layer to that which was previously described as 1 76 in FIG. 58.
  • FIG. 60 one has to imagine removing the exploded active electrode view layer 1 76 in FIG. 58 and replacing it with the active electrode 1 76'.
  • the active electrode plate 1 76' itself is not much different from that previously illustrated in FIG. 58 (its surface area is slightly smaller).
  • a grounded or third shield trace 224 has been deposited around the active electrode 1 76' on the same co- planar surface.
  • the purpose of the surrounding grounded shield trace 224 on the same plane as active electrode 1 76' is to further aid in the coaxial shielding of the active electrode plate 1 76'.
  • the active electrode 1 76' When one considers that the active electrode 1 76' is already sandwiched between grounded shield plates 1 94 and 1 94', this means that it is now shielded top, bottom and on both sides.
  • the addition of the optional edge shield 224 prevents edge radiation of high frequency from the shielded three-terminal flat-through EMI/energy dissipating filter 1 90.
  • the filter performance of the flat-through capacitor can be further improved by additional low-pass circuit elements. Referring to FIG. 61 , one can see that the active electrode plate 1 76" has been modified by adding a Wheeler spiral inductor element 1 58. Wheeler spiral inductors are well known in the prior art for a variety of other applications. Wheeler spiral design equations are also readily available.
  • the spiral inductor circuit trace 1 58 adds substantial series inductance to the active electrode plate 1 76" and also increases the flat- through capacitance overlap area (ECA) as well.
  • ECA flat- through capacitance overlap area
  • Fig. 61 by also having a wide active electrode plate area 1 76", one also maximizes the parasitic flat- through capacitance as previously described.
  • the increased total effective overlap area (ECA) between the inductor circuit trace of 1 58 and the active electrode plate 1 76" as they are sandwiched between the two ground shield plates 1 94 and 1 94' greatly increases the flat-through capacitance Cp and Cp'.
  • FIG. 62 illustrates a quadpolar filtered feedthrough assembly in accordance with the present invention. It is very similar in construction as previously described for the unipolar device of FIGS.
  • ground electrode shield plates 1 94, 1 94' and 1 94" Sandwiched between these ground electrode shield plates are active circuit electrode layers 226 and 228.
  • Flat-through electrode circuits 1 76 and 1 76' are contained on electrode circuit trace layer 226.
  • parasitic capacitances or flat-through capacitances are formed due to the ECA overlap area on both sides.
  • the spacing of the ground shields 1 94 and 1 94' is quite important in that they should not be spaced too far apart or high frequency RF leakage could occur due to the electromagnetic interference signals re-radiating from the flat-through electrode plates 1 76 and 1 76' out through the outside edge.
  • This RF leakage was prevented in the unipolar design of FIG. 54 by wrapping the metallization surface 208 around the outside. This can also be accomplished by stitching through a number of conductive filled via holes 230 as shown in FIG. 64.
  • FIG. 64 is a modification of the ground shields 1 94-1 94" of FIG. 63. One can see that there are a plurality of these stitching vias 230 or grounding vias all around the perimeter and even inside.
  • stitching vias 230 The purpose of these stitching vias 230 is to electrically connect the three (or nj ground shield layers 1 94-1 94" together in a multi-point low inductance configuration.
  • These stitching vias form another very important purpose in that they decrease the effective length when one looks at the side view of this laminated sandwiched structure. It is a common principle in waveguide engineering that the cutoff frequency of a waveguide is dependent upon its geometry. For rectangular waveguides, the length-to-width ratios are very important. By shortening the length, one greatly increases the frequency at which the waveguide could start to pass electromagnetic signals through it.
  • ECA effective capacitance area
  • FIG. 65 Another way to accomplish this is shown in FIGURE 65, by the use of slot patterns 232.
  • FIG. 65 there are multiple slots 232 as shown. These slots can be placed in a number of areas. The slots 232 are generally not filled in the same way that a via hole is filled. However, it does allow the adhesive binder layers to contact through the metalized electrode shield. For example, in a typical polyimide flex cable arrangement, multiple layers of polyimide are laid up with an acrylic binder.
  • the acrylic binder can contact the underlying substrate material 234.
  • the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention were used at the point of lead wire ingress of a cardiac pacemaker, then the active electrodes must be low loss in order to conduct both the pacemaker pacing pulses and also conduct the biologic sensing signals.
  • a modern cardiac pacemaker actively detects and monitors the electrical activity of the heart.
  • One purpose for low loss active electrodes is as an AIMD battery saving purpose.
  • Some patients are not pacemaker dependent, meaning that they only need to be paced at certain critical times when their heart rate drops too low. Therefore the pacemaker electronic circuits constantly monitor the heart.
  • the pacemaker activates and delivers the pacing pulse through implanted leads to the appropriate cardiac tissue.
  • the stimulation pulse then restores the heart to its natural sinus rhythm. Accordingly, it is very important that the active electrodes, such as those shown in Iayer226 and 228 of FIG. 63, be relatively low loss.
  • FIGURE 66 illustrates a methodology of putting multiple holes 236 in the metalized electrode shield. These multiple holes 236 serve the same purpose as the previously described slots 232 in FIG. 65.
  • FIGURE 67 shows an alternative arrangement for the active electrode layer 226 previously shown in FIG. 63. In FIG. 67, one could imagine that this layer 226' could replace layer 226 in FIG. 63.
  • FIGURE 68 is a graph illustrating attenuation versus frequency comparing the performance of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of FIG.
  • Fig. 68 the feedthrough capacitor and the MLCC are of equal capacitance value.
  • the capacitance value of the shielded three-terminal flat-through EMI/energy dissipating filter is significantly less.
  • the feedthrough capacitor exhibits a small self-resonant dip shown as SRFi . Feedthrough capacitors are unique in that after they go through this type of transmission line self resonance, they continue to function as a very effective broadband filter.
  • the flat- through capacitance in the present invention is a parasitic capacitance and it tends to be a relatively low capacitance value. That means that its effective 3 dB point (or point where it starts to become an effective filter) is relatively high in frequency. In this case, the 3 dB point is approximately 1 000 MHz.
  • FIG. 68 illustrates the composite or added response attenuation curve (which for active electrode 1 76 is the addition of all of the capacitive elements in parallel illustrated in FIG. 59 (parasitic inductances L p are so small in value that they can be ignored).
  • An effective way to increase the capacitance value of the parasitic capacitor is to increase the dielectric constant of the surrounding dielectric materials.
  • a high dielectric constant (k) dielectric such as barium titinate or strontium titinate for the insulative substrate material 234.
  • the value of the flat-through capacitance would go up so high that one would not even need to include the MLCC capacitance.
  • Another way to accomplish the same thing and to use lower cost materials would be to use flex cable technology, such as polyimide or Kapton flex as previously described.
  • the dielectric constant of these materials is relatively low (typically below 10).
  • one way to make up for this would be to increase the effective capacitance area in the overlap area of the active electrode plates 1 76 and their surrounding sandwiched ground shields 1 94 and 1 94' (and/or reduce the dielectric thickness, d).
  • FIGURE 69 is an exploded view of the quadpolar hybrid EMI filter of the present invention that is similar to that previously shown in FIG. 63.
  • the circuit layers 226 and 228 of FIG. 63 have been modified to add inductor traces 1 58 - 1 58'". These inductor traces are included as part of and are in series with active electrodes 1 76 - 1 76'". It will be obvious to those skilled in the art that one would most likely select one inductor pattern and stay with that.
  • electrode plate 1 76 there is a rectangular Wheeler spiral inductor 1 58.
  • electrode plate 1 76' we have by way of example, an inductor meander 1 58' which can be one of many patterns, including those illustrated in FIGURE 74.
  • electrode plates 1 76" and 1 76' we have round Wheeler spiral inductors 1 58" and 1 58'" as shown.
  • Embedding co-planar inductors in series with the active electrodes is virtually a no-cost addition. The reason for this has to do with the manufacturing methods typically employed to produce flex cables or even solid substrates. That is, a solid metal layer is laid over the entire surface by plating or other metal-deposition processes and then resistive materials are laid down by silk-screening or similar processes. Then chemical etchings are used to remove all of the metal except for the desired electrode patterns.
  • adding inductor elements 1 58 - 1 58'" as shown in FIG. 69 becomes very inexpensive and easy to do.
  • Advantages of adding the inductors as shown in FIG. 69 include making the low-pass EMI filter from a single element into what is known as a dual element L-section low-pass filter.
  • a dual element filter has a steeper attenuation slope and is therefore more efficient.
  • FIGURE 70 is very similar to FIG. 69 except that the active electrode trace layers 226" and 228" have been modified by adding an optional surrounding co-planar ground shield 224.
  • This surrounding ground shield concept to prevent substrate edge re-radiation was previously described in relation to FIG. 60.
  • an optional co- planar ground shield 224' has also been disposed on layers 226" and 228" between each of the active electrode traces 1 76 and 1 76' and also 1 76" and 1 76'".
  • layer 226" of FIG. 70 one can see a co- planar ground shield 224' that is disposed between circuit traces 1 76 and 1 76'.
  • the cross-talk shield 224' also need not be used on all active electrode layers in a particular shielded three-terminal flat- through EMI/energy dissipating filter 1 90, but only in those layers where crosstalk is a concern between adjacent circuits. In other words, the cross-talk shield 224' may be used on layer 226" but not be needed on layer 228". It will be obvious to those skilled in the art that on a particular substrate layer, that the number of circuit active electrodes (and optional cross-talk shields) is not limited to two (such as 1 76 and 1 76' as shown in FIG. 70), but can be of any number, n.
  • FIGURE 71 is yet another alternative to the quadpolar shielded three-terminal flat-through EMI/energy dissipating filter 1 90 as previously described in relation to FIG. 70.
  • the difference between FIG. 70 and FIG. 71 is the addition of a feedthrough capacitor 1 32 which is bonded to the hermetic terminal 1 1 2 by way of an insulative adhesive washer 200.
  • Feedthrough capacitors 1 32 are well known in the prior art and provide very effective high frequency filtering.
  • FIG. 71 illustrates that these prior art feedthrough capacitors can be used in combination with the novel shielded three-terminal flat-through EMI/energy dissipating filter technology of the present invention.
  • MLCC capacitors 1 42-142' would allow for the elimination of the MLCC capacitors 1 42-142'" as illustrated (or they could be replaced by higher value MLCCs, film chip capacitors, tantalum technology or the like).
  • one could use a monolithic ceramic feedthrough capacitor as illustrated in FIG. 71 along with the shielded three-terminal flat-through EMI/energy dissipating filter technology and surface mounted very high capacitance value tantalum capacitors.
  • EAS electronic article surveillance
  • RFID readers in the 1 25 to 1 32 KHz or 1 3.56 MHz range.
  • EAS gates are the pedestals that a person, including a pacemaker patient, typically encounters when exiting a retail store. These detect tags on articles and goods such as to prevent theft.
  • One common system is manufactured by Sensormatic which operates at 58 kHz. It has been demonstrated through numerous publications that these EAS gates can interfere with pacemakers and ICDs.
  • the present invention as illustrated in FIG. 71 would be effective in attenuating signals at 58 kHz all the way up through cell phone frequencies in the GHz range.
  • FIGURE 72 is a blown up view of the round Wheeler spirals 1 58" and 1 58'" of FIG. 69.
  • FIGURE 73 is a square Wheeler spiral which is very similar to the rectangular Wheeler spiral 1 58 previously shown in FIG. 69.
  • FIGURE 74 shows some typical inductor meander shapes 1 58'. It will be obvious to those skilled in the art that any number of different inductor shapes can be easily deposited on the same co-planar substrate layer in series and an integral part of the active electrode plate(s) 1 76 of the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 technology of the present invention.
  • FIGURE 75 illustrates the attenuation curves for various types of low-pass filters.
  • a typical MLCC capacitor curve is shown.
  • the MLCC undesirably goes through a self resonant frequency SRF after which its attenuation declines versus frequency (the MLCC undesirably becomes increasingly inductive).
  • SRF self resonant frequency
  • the MLCC undesirably becomes increasingly inductive.
  • the EMI/energy dissipating filter of the present invention one achieves broadband filter performance all the way up to and including 1 0 GHz.
  • a single element or C section filter has an attenuation slope of 20 dB per decade.
  • the attenuation slope increases to 40 dB per decade.
  • a third element which makes the filter into either a ⁇ or T section, increases the attenuation slope to 60 dB per decade.
  • a double L which is shown as a LLi or an LL2, meaning that the inductor can point either towards the body fluid side or to the device side, has an attenuation slope of 80 dB per decade.
  • a 5-element filter will have 1 00 dB per decade attenuation slope. It will be obvious to those skilled in the art that any number of elements could be used.
  • the structure shown has an electrical schematic as shown in on FIG. 62 as an L section circuit.
  • the capacitance of this L section consists of the sum of the parasitic flat-through capacitance Cp which is formed between the active electrode plate 1 76 including the ECA formed from the inductors 1 58, and the opposing grounded shields 1 94 and 1 94'.
  • the MLCC capacitor 1 42 in FIG. 62 represents the capacitors 142-1 42'" surface mounted onto the hybrid substrate 1 92.
  • the MLCC capacitor is effective up to its resonant frequency; however, that is where the flat-through capacitance takes over yielding the relatively smooth curve shown in FIG. 75 for the L section filter.
  • the L section could be reversed.
  • the inductor spiral could be designed and put on the other side of the capacitor as opposed to towards the body fluid side as presently shown in FIGS. 61 and 62.
  • multiple inductors could be placed inside of the novel hybrid substrate 1 92 in order to form a " ⁇ ", "T", “LL” or even a "5" or "n” element device.
  • the present invention includes a new method of constructing prior art low-pass EMI filter circuits that are already well known in the art.
  • the feedthrough capacitor, the L, the ⁇ , the T and LL filters are already well known.
  • FIGURE 76 is a family of filter attenuation curves similar to that previously shown in FIG. 68.
  • the 3 dB cutoff point or the point at which the flat-through (Cp) curve of the shielded three-terminal flat-through EMI/energy dissipating filter starts to become effective, has been moved substantially downward in frequency (to the left). In this case, its 3 dB point is approximately 40 MHz.
  • the composite curve of the shielded three-terminal flat-through EMI/energy dissipating filter with the surface mounted MLCC(s) out performs (has higher attenuation than) the referenced prior art feedthrough capacitor.
  • the amount of improvement is very substantial. For example, at MRI frequencies which are 64 MHz for 1 .5 Tesla machines and 1 28 MHz for 3 Tesla machines, there is an improvement anywhere from 1 0 to over 20 dB. This is very significant and very important to protect an active implantable medical device from interference during an MRI scans.
  • FIGURE 77 illustrates a bipolar hermetically sealed hybrid substrate filter 1 90 of the present invention.
  • FIGURE 78 is an exploded view of the internal layers taken along line 78-78 in FIG. 77.
  • active electrode plates 1 76 and 1 76' the square Wheeler spirals 1 58 and 1 58' have been greatly enlarged.
  • the grounded shield plates 1 94-1 94" it is essential that they be properly grounded via electrical connection material 21 0-21 0" to the gold braze ring 1 24 of the ferrule 1 20 of the hermetic seal 1 1 2 as shown in FIG. 77.
  • ferrule 1 20 is typically of titanium, stainless steel or suitable non-corrosive material. Unfortunately, during manufacturing or over time, titanium can build up undesirable oxides.
  • FIGURE 79 is an alternative embodiment showing the hybrid substrate 1 92 of the present invention designed to be inserted partially into the ferrule 1 20 of the hermetic seal assembly 1 1 2 as shown in exploded view.
  • 1 39"" would be a ground pad, and pads 1 39-1 39'" would be circuit connections.
  • the MLCC capacitors 1 42-1 42' as previously described, would connect from the active electrodes plates (not shown) of the shielded three-terminal flat-through EMI/energy dissipating filter through vias internally to internal grounded shield plates (also not shown).
  • the MLCC capacitors 142-1 42'" would not be required. Also shown is an optional embedded Wheeler spiral inductor 1 58. There would be one of these in series with each of the MLCC capacitors 1 42- 1 42'" as previously described.
  • a shield ring 242 is provided so that it will be connected through laser welding, brazing, soldering or the like to the ferrule 1 20. This is important so that electromagnetic interference cannot directly penetrate through the insulator 1 1 8 and re-radiate to the interior of the electronic device (a hermetic insulator forms a hole in the titanium electromagnetic shield housing of a cardiac pacemaker).
  • the shield ring 242 is connected via soldering to via holes to the internal ground shield plates of the shielded three-terminal flat-through EMI/energy dissipating filter structure.
  • Connection pads 240 through 240'" are designed to be electrically connected to lead wires 1 1 4 through 1 1 4 '".
  • FIGURE 80 is a partially fragmented view taken from FIG. 79.
  • the leads 1 14" and 1 14"' are typically welded, brazed or soldered 244 and 244' into the lead wire retaining blocks 240" and 240'" as shown.
  • This electrical connection makes contact to the internal grounded shield plates (not shown) of the hybrid substrate 1 92.
  • the electrical connection material 246 and 246' not only makes contact to the titanium flangel 20, but it also makes intimate contact to the gold braze 1 24 such that there is an oxide free electrical connection in order to guarantee high frequency performance.
  • the electrical connection material 246 and 246' not only makes contact to the titanium flangel 20, but it also makes intimate contact to the gold braze 1 24 such that there is an oxide free electrical connection in order to guarantee high frequency performance.
  • the metallization area 247 forms a circumferential ring over the non-conductive insulator 1 1 8 such that re-radiation of EMI through the hermetic seal 1 1 2 is prevented.
  • FIGURE 81 is the electrical schematic diagram of the quadpolar hybrid EMI filter of FIGS. 79 and 80.
  • FIG. 81 illustrates an L-section low-pass filter.
  • FIGURE 82 illustrates an inline hybrid substrate 1 92 of the present invention.
  • back-to- back MLCC capacitors 142 and voltage suppression diodes 248 also known as zener diodes
  • voltage suppression diodes 248 also known as zener diodes
  • FIGS. 82 and 83 there can be another inductor (optional) L2 that would be embedded within the hybrid substrate 1 92 and an additional flat-through capacitance Cp' before one reaches the electrical connection pads A through F as illustrated.
  • the inductors for example inductor Li a and L2a, could be constructed of square, rectangular or a round Wheeler spirals or any of the other meander shapes previously described.
  • FIG. 83 illustrates a very efficient five element low-pass filter.
  • FIGURE 84 illustrates another form of the novel hybrid substrate 1 92 of the present invention.
  • the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 includes a hybrid substrate 1 92 is divided into two sections: 1 92' and 1 92".
  • Section 1 92' is a relatively thin area of flex cable and is therefore very flexible.
  • Section 1 92" can be made of similar or same materials as section 1 92' (or it can be a rigid board or substrate to which flexible section 1 92' is connected), but its thickness is built up until it forms what is known in the art as a section of "rigid" cable.
  • This rigid section 1 92" could be of polyimide, Kapton or other typical flex cable construction.
  • the flex cable section 1 92' is designed to slip down over the pins 1 14-1 1 4'" of a hermetic seal 1 1 2 of an AIMD or any other electronic device (hermetic or not), such as those typically used in telecommunications, consumer electronics, military or even space applications).
  • the hermetic seal 1 1 2 can be any type of terminal, including non-hermetic terminals or even plastic terminals.
  • the present invention is applicable to any electronic assembly or a point at which any lead wires ingress and egress an electronic assembly, subassembly or housing. The methods of attachment to the terminal pinsl 1 4-1 14'" of the hermetic seal 1 1 2 and to the ground pin 1 96 will be described in connection with subsequent drawings.
  • FIG. 84 Referring now to the rigid section 1 92", one sees that a number of passive or active surface mounted electronic components can be mounted (they can also be embedded which is also well known in the prior art of multilayer substrate design).
  • the hybrid substrate 1 92 of FIG. 84 has been designed with convenient lead wires 204-204'" and 1 96 for easy connection to lands of a circuit board 250 perhaps with an integrated circuit or microchip 252 within the active implantable medical device.
  • the circuit board 250 is not part of the present invention, but is important in that the present invention be capable of connecting and interfacing with it.
  • FIGURE 85 is very similar to FIG. 84 except the diode array Di has been replaced with either a passive or an active RFID chip (RFID).
  • RFID active RFID
  • the RFID chip would operate in the International Standards Organization band of 1 25 to 1 35 kHz.
  • the RFID chip could be used for a number of different purposes, including identification of the model number, serial number of the AIMD, important patient or implanting physician information and the like. See U.S. Patent Application Publication No. US 2006-021 2096 Al , the contents of which are incorporated herein by reference.
  • the RFID chip as illustrated in FIG. 85 could be simply mounted but not electrically connected to the active electrodes of the shielded three- terminal flat-through EMI/energy dissipating filter. No electrical connections are required for a passive RFID chip. In other words, when an external interrogator/reader was used, a powerful electromagnetic field would activate an antenna within RFID chip and it would automatically use the received power to turn on its microchip and transmit a return pulse.
  • the RFID chip, as shown in FIG. 85 could be electrically connected to power circuits embedded within the shielded three-terminal flat-through EMI/energy dissipating filter such that it received power from the internal battery of the AIMD. In this case, it would be known as an active RFID chip.
  • the RFID chip With an active (powered) RFID chip, it could embody a much more sensitive receiving circuit and also transmit a much more powerful return pulse.
  • the RFID chip as shown in FIG. 85 could be used as a wake-up feature for AIMD RF telemetry circuits.
  • the external programmer would become active and electrograms and other important information would be displayed.
  • the wand would be right against the patient's skin surface or at most a couple of centimeters away.
  • distance RF telemetry is becoming increasingly common.
  • a high frequency antenna that would be embedded within the plastic header block of the AIMD (outside the EMI shielded titanium housing). This would communicate with an external RF receiver-transmitter programmer.
  • a typical band for such communication would be in the 402 to 405 MHz (known as the MICS band).
  • Other devices use even higher frequencies for distance RF telemetry.
  • the Zarlink chip uses a higher frequency (in the GHz range) to wake-up the lower frequency RF telemetry circuit.
  • the higher frequency is more efficient; however, the device or chip still consumes an amount of idling energy from the AIMD battery to always be alert for its wake- up call.
  • a passive RFID chip is used as a wake-up feature. This RFID can be integrated into the hybrid substrate 1 92 of the present invention (or mounted anywhere else inside or outside the housing of the AIMD).
  • the external RF programmer can incorporate a low frequency RFID reader which would transmit a signal which would penetrate right through the titanium housing of the AIMD and activate the embedded passive RFID chip.
  • the circuitry of the RFID chip would be connected to the telemetry circuits contained within the AIMD.
  • the external programmer would send the RFID signal as a wake-up call to turn on the telemetry receiving circuits so that the pacemaker could communicate with the external programmer.
  • FIGURE 86 is very similar to FIG. 84. In this case, toroidal inductors L3-L3'" have been used to replace the surface mount chip inductors . Chip inductors are low in both their inductance value and their current rating.
  • Chip inductors can be acquired in two main forms: a) with a ferrite core and; b) without a ferrite core.
  • a) with a ferrite core and; b) without a ferrite core For exposure in magnetic resonance imaging applications, it is usually desirable to eliminate ferrite material as it will saturate due to the main static field of the MR scanner. See U.S. Patent Application Publication No. US 2007-01 1 2398 Al and U.S. Patent No. 7,363,090, the contents of which are incorporated herein.
  • FIG. 86 one can see that the toroidal inductor L3' does have a ferrite core TC with many turns of wire W wrapped around it. This makes for a very large inductor value.
  • the inductance would drop to a very low value due to the saturation of the ferrite element TC itself. It is a feature of the present invention that the ferrite element would be selected so that it would not exhibit permanent remnants. That is, once the device was removed from the magnetic resonance (MR) scanner, the magnetic dipoles would return to their scattered state and the inductor would continue to operate as previously intended.
  • the purpose of the toroidal inductors L3-L3'" would be to provide a very high inductance value for a low-pass filter so that its 3 dB cutoff frequency would be very low in frequency (for example, below 1 MHz or even down to 58 kHz for EAS gates).
  • inductor chips could also be large value wound inductors with powdered iron or ferrite toroidal cores.
  • electromagnetic field environments are quire harsh, but are also well known.
  • the pulsed RF field is at 64 MHz.
  • the shielded three-terminal flat- through EMI/energy dissipating filter could be designed such that its parasitic flat-through capacitance along with MLCC capacitors C2 would provide sufficient attenuation at 64 MHz so that the AIMD could be free from EMI and be operated safely in an MR scanner.
  • the cores of the toroidal inductors 1 56 saturated and that low frequency filtering is thereby not available during the time of the MR scans.
  • a person in an MR scanner is not likely to encounter an EAS gate or RFID reader typically found when exiting retail stores. What is important is that after the patient is removed from the MR scanner is that the toroidal inductors (or chip inductors with ferrite cores or layers) not exhibit permanent remnance and return to their original state so that they will continue to provide effective low frequency filtering against emitters that the patient may find in their every day environment.
  • FIGURE 87 illustrates the flexibility of section 1 92'. As one can see, it is very easy to bend the entire flex section 1 92' into a right angle. This is important so that the entire assembly can easily fit inside the typical spaces and geometries of active implantable medical devices, including cardiac pacemakers and the like.
  • FIGURE 88 is an internal sectional diagrammatic view taken of the hybrid substrate 1 92 of FIG. 84.
  • FIG. 88 one can see that the gold braze 1 24 of the hermetic seal 1 1 2 is shown on the left.
  • An electrical connection BGA is made between internal ground via V to shield plates 1 94 and 1 94' and the gold braze material 1 24.
  • These electrodes/RF shield plates 1 94 and 1 94' extend full width throughout the flexible portion 1 92' and the rigid portion 1 92" as illustrated in accordance with the present invention.
  • Other circumferential via holes V (not shown) are used to provide a low impedance attachment to additional points between ground shield plates 1 94 and 1 94' to the gold braze 1 24 of the hermetic seal as shown.
  • this parallel combination of inductor chip 1 56 and chip capacitor 142 form a parallel combination which is electrically in series with active electrode plate 1 76 in accordance with the referenced co-pending patent serial numbers.
  • MLCC 1 42 and inductor chip 1 56 placed on opposite sides (top and bottom) of the hybrid substrate 1 92 is just one way to form the parallel resonant combination.
  • FIGS. 80, 85 or 87 of U.S. Patent Application Publication No. US 2007- 01 1 2398A1 any of these novel integrated L-C chips could be used as a single element on top (or the bottom) of hybrid substrate 1 92 that would replace both MLCC 142 and inductor 1 56.
  • the parallel bandstop filter formed by Ci and Li can be placed anywhere in the active electrode circuit of the shielded three-terminal flat-through EMI/energy dissipating filter. In other words, it could be moved further to the right, for example, after L2 or even after L3. It will also be obvious to those skilled in the art that any combination of circuit elements is possible, including placing circuit elements 1 42 and 1 56 in series as an inductor-capacitor (L-C) trap filter anywhere between the active electrode 1 76 and ground 1 94, 1 94'.
  • L-C inductor-capacitor
  • active electrode plate 1 76 is then routed through via hole W through inductor l_2 and then back down through via hole V ⁇ back to active electrode plate 1 76.
  • Active electrode plate 1 76 is then electrically continuous to another via hole Vg which is connected to the right hand termination surface of MLCC capacitor C2.
  • the other termination end of the capacitor C2 is connected through via hole V 4 to grounded shield substrates 1 94-1 94'". This makes for a very low impedance RF ground connection for capacitor C2.
  • the active electrode plate 1 76 then continues to via hole Vi 0 and up and to the right through inductor L3 whose other end termination returns through via hole Vn putting L3 in series with active electrode plate 1 76.
  • inductors L2 and L3 can be chip inductors, including ferrite chip inductors or they can be toroidal wound inductors or other types of inductors.
  • Active electrode plate 1 76 is then connected through via hole V12 to the right hand side of the high voltage suppression diode array Di .
  • the left hand side of the diode array Di is connected through via hole V13 such that it makes connection with grounded shield plates 1 94-1 94'".
  • Active electrode plate 1 76 then exits to the right from via hole V12 over to via hole Vi 4 and then up to wire bond pad 1 38 which is very convenient for connection of lead wire 204 as shown.
  • a ground pad GP on top of the hybrid substrate 1 92 has been provided which connects by via hole Ve to the embedded grounded shield plates 1 94-1 94'".
  • ground wire 1 96 which has been connected to the bond pad area GB. This is not required for all AIMDs, however, it is a very convenient point for connection of integrated circuit substrate 250 ground circuit trace or traces to the housing of the AIMD via lead 1 96 and then to the ground shield plates 1 94, 1 94' of the hybrid flex shielded three-terminal flat-through EMI/energy dissipating filter.
  • the ground shield plates are connected to the gold braze 1 24 of the hermetic seal 1 1 2 which is typically laser welded into the overall titanium housing/can of the AIMD (shown as 300 in FIG. 1 14).
  • the housing can act as an EMI shield, an electrode or an energy dissipation surface.
  • a low impedance RF ground is required which is accomplished by the grounded shield plates of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention.
  • FIGURE 89 is the schematic diagram of the novel hybrid substrate 1 92 of FIG. 84. For example, tracing one of the quadpolar circuits through, for example the circuit labeled 1 76, point "a" is toward the body fluid side of the lead wire 1 14 that connects from the hermetic seal 1 1 2 shown in FIG. 84.
  • the active electrode plate 1 76 enters the bandstop filter BSF which consists of the parallel inductor Li and MLCC capacitor Ci , one sees that we have now entered the shielded part of the substrate meaning that the entire active electrode plate 1 76 is contained within grounded shield plates 1 94 and 1 94'After exiting the bandstop filter BSF, 1 42,1 56, we then go through inductor L2, and then MLCC capacitor C2 is connected to ground 1 94, 1 94'. MLCC C2 is then connected with inductor L3. After active electrode 1 76 exits inductor L3, it is still shielded/sandwiched within the ground plates 1 94, 1 94' of the hybrid substrate 1 92.
  • Diode array DA In this case, the diode array is shown connected to ground and acts as a high voltage suppression device.
  • Diode arrays DA of this type are commonly used in AIMDs. The reason for this has to do with the use of either ICDs or automatic external defibrillators (AEDs). AEDs are now commonly deployed in government buildings, hotels, airplanes, and many other public places. These life saving devices are very important. If a person is unconscious, the AED electrodes are placed on the person's chest. The AED then automatically detects dangerous ventricular arrhythmias (such as ventricular fibrillation) and then an automated high voltage biphasic shock is applied to the electrodes.
  • ICDs automatic external defibrillators
  • the implanted leads pick up this high voltage shock that is being used to cardiovert the cardiac tissue. Since the implanted pacemaker is a low voltage device, this high voltage shock can damage sensitive internal circuits of the cardiac pacemaker. Accordingly, diode arrays, incorporating back to back diodes, zener diodes, TransorbsTM or the like are commonly used to short the high voltage spike to ground before it can damage sensitive active electronic circuits (such as integrated circuits, hybrid chips and the like).
  • the diode array that's typically used takes up a lot of space on the circuit board, it is a feature of the present invention that it could easily be integrated into the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention to save space by placing it on the interconnect circuit.
  • Another way to think of the schematic diagram shown in FIG. 89 is that what we have is a bandstop filter for suppression of MRI or other powerful single frequency emitters in series with a three element T section filter as previously described in connection with FIG. 73 in series with a high voltage suppression diode.
  • bandstop filter could be located to the right of the C, L, ⁇ , T or ⁇ element filter. It could also be placed in combination with L-C trap filter to ground. Accordingly, one can see that a number of components have been assembled into one convenient package.
  • FIG. 84 there are a number of other features of the novel hybrid flex substrate 1 92 that need to be pointed out.
  • One of the features is best described by referring back to FIG. 84 wherein the via holes have an enlarged rectangular portion A, B, C and D for suitable electrical probing or electrical testing.
  • This section allows for a robot or a pogo spring connector to be placed on the pad to facilitate electrical testing, accelerated life testing, burn in, insulation test, dielectric withstanding voltage test or other suitable electrical tests as needed. These tests, often performed at elevated temperatures, are essential to assure the long term reliability of the novel shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • a similar enlarged pad area(s) 1 39 has been provided for similar electrical contact for test instruments as previously described.
  • the entire hybrid flex substrate 1 92 be laid flat as is shown. Being laid flat is particularly suitable to be placed into fixtures for modern robots. These robots are typically fed by tape and reel components or trays which house all of the electronic components. By having the basic hybrid substrate 1 92 laying flat, all of the components can be quickly placed by the robots. Assembly by hand is impractical due to the small size of the surface mounted components.
  • the MLCC chips can be 0201 or smaller which is the size of a grain of pepper (.020 inch by .ol 0 inch).
  • the inductor l_2 will preferably be of a non-ferrite core and the capacitor C2 would be of sufficient value working in conjunction with flat- through capacitance Cp such that those components alone would provide adequate protection at MRI pulsed frequencies.
  • the RF pulsed frequency is 64 MHz.
  • inductor L3 As illustrated in FIG. 86, one can provide a very high degree of (attenuation) immunity to low frequency emitters, such as 58 kHz electronic article surveillance (security) gates that are typically used in retail stores. In addition, one can provide a great deal of immunity to low frequency (LF) RFID readers. These are typically used for automotive keyless entry systems and the like. Since neither RFID readers nor store security gates are present in an MR scan room, it does not matter if inductor L3' does saturate in the MR environment.
  • LF low frequency
  • capacitor elements C2 could be a monolithic ceramic capacitor (MLCC), or a very high value aluminum electrolytic or tantalum capacitor.
  • MLCC monolithic ceramic capacitor
  • a capacitor of several microfarads could be used with a toroidal wound inductor of several hundred microhenries. This would provide attenuation down to very low frequencies.
  • FIGURE 90 is an electrical schematic for one circuit A of FIG. 86.
  • the T circuit low-pass filter has been replaced with a Pl circuit low- pass filter consisting of C2, L2 and C3.
  • the bandstop filter BSF consisting of components Li and Ci acting in parallel, has been replaced by a L- C trap filter consisting of Li and Ci that are wired in series to ground 1 94, 1 94'. It is well known that when L-C series components are in resonance, they ideally form a short circuit at the resonant frequency. This is more thoroughly described in U.S. Patent 6,424,234 the contents of which are incorporated herein. Referring once again to FIG.
  • the use of a trap filter would be particularly advantageous if the AIMD were to be exposed to a magnetic resonance imaging environment.
  • the trap filter could be designed to be resonant at 64 MHz. This would short out 64 MHz signals to ground (the titanium housing of the AIMD). This would not only provide a great deal of immunity and protection to device electronics, it would also desirably short MR energy to the metallic housing of the AIMD such that it cannot reflect back and cause overheating of the distal electrode tip to tissue interface. Using the housing to dissipate energy is described in U.S. Provisional Patent Application Nos.
  • the Pl ( ⁇ ) circuit could consist of an MLCC capacitor C2 which would be very effective at high frequencies.
  • L2 could be a toroidally wound inductor with a ferrite core as previously described as L3' from FIG. 86.
  • C3 could be a high value tantalum capacitor. It would not matter if the Pl circuit was effective while the AIMD was operating in a MR scanner. This is because the L-C trap would be made of components which do not saturate in a magnetic field environment. In other words, inductor Li would be non-ferromagnetic and capacitor Ci would generally be of MLCC construction.
  • the EMI filtering immunity for the MR environments would consist entirely of the operation of the trap filter operating in combination with the parasitic capacitance (flat-thru capacitance) of the novel hybrid substrate 1 92 of the present invention. Accordingly, the Pl section filter would be very effective when the patient is outside of MR environments for attenuating low frequency signals and signals throughout the frequency range.
  • the structure as illustrated in FIG. 90 would perform effective filtering from approximately 30 kHz all the way to 1 0 GHz while outside of an MR environment. While in an MR environment, it would perform effective filtering at selected frequencies of one or more trap filters as shown.
  • trap filter Only one trap filter is shown, but it will be obvious to those skilled in the art that any number of trap filters could be placed in parallel in order to short circuit multiple RF frequencies. For example, if one were to want the AIMD to be compatible with both 1 .5 and 3 Tesla scanners, then two trap filters would be required; one resonating at 64 MHz and the other one at 1 28 MHz.
  • the L-C trap filter can each be separated by a series bandstop filter consisting of a capacitor in parallel with an inductor so that the components of each individual trap filter do not interact with each other.
  • 61 /1 44,1 02 which describes a number of other frequency selective circuits that can be used to balance the energy during MRI scanning.
  • the objective is to take as much energy off the implanted lead system and shunt it to the conductive housing of the AIMD which then becomes its own energy dissipating surface. It will be obvious to those skilled in the art that any and all of the schematics that are disclosed in U.S. Provisional Patent Application Serial No. 61 /1 44,1 02 can be embodied in the novel hybrid substrate 1 92 of the present invention.
  • FIGURE 91 is very similar to FIGS. 84, 85 and FIG. 86. The difference is that a prior art feedthrough capacitor 1 32 is being used in conjunction with the hybrid substrate 1 92 of the present invention. Feedthrough capacitors are well known in the prior art, including U.S. Patent Nos. 4,424,551 ; 5,333,095; 5,905,627; and 6,765,779, the contents all of which are incorporated. Referring once again to FIG. 91 , the feedthrough capacitor 1 32 would provide high frequency filtering generally in the frequency range from 1 00-10,000 MHz. As described for FIG.
  • FIGURE 92 illustrates the reverse side of the flexible portion 1 92' of the hybrid flex from FIG. 84.
  • a robot has dispensed a circular portion of thermal-setting conductive thermal setting adhesive 254. This is designed to align precisely with the gold braze 1 24 of the hermetic terminal 1 1 2 of FIG.
  • the entire substrate can be laid down over the hermetic terminal assembly 1 1 2 and then the thermal-setting conductive material 254 can be cured in an oven, furnace or other equivalent process.
  • FIG. 92 one will see that there are gaps left in the circumferential thermal-setting conductive polymer 254. These gaps are present to allow for a free flow of helium during fine leak detection as previously described.
  • FIGURE 93 is a sectional view taken along line 93-93 from FIGS. 84 and 92.
  • Alternative methods of performing this low impedance RF electrical ground connection to the grounded shield plates 1 94, 1 94' of the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention are illustrated in FIGS. 94 through 97.
  • FIGURE 94 illustrates a methodology of pushing a resistance welding electrode pad 256 onto a flex cable rivet eyelet 258 thereby creating a current flow in which results in an elevated temperature sufficient to reflow a low temperature braze 260 solder or the like to the gold braze material 1 24.
  • FIGURE 95 illustrates an outer pin 262 which has been laser welded to the ferrule 1 20. The minimum number of pins is one, but an optimal number would be four to six to provide suitable RF connection to the internal grounded shield plates 1 94 and 1 94' of the present invention.
  • An alternative method is shown in FIG.
  • FIG. 97 Another RF ground attach methodology is shown in FIG. 97 whereas the ferrule 1 20 is of a pressed powder metallurgy.
  • a pedestal pin 268 (4 to 6 or more is the ideal number of pedestals) is formed as part of the powder metallurgy process.
  • all the materials would be typically of titanium which is ideal for this purpose.
  • a gold sputtering 270, plating or brazing is placed over the terminal pedestal 268 such that a proper oxide-free electrical connection can be made to the hybrid substrate 1 92 of the present invention.
  • FIGURE 98 shows a modified version of the flexible portion 1 92' of the flex cable assembly of FIG. 84 with four (or more) via holes VH suitable for placement over any of the embodiments described in FIGS. 95 through 97 for electrical attachments to its grounded shield plates 1 94 and 1 94'.
  • FIGURE 99 illustrates a cross-section 99-99 from FIG. 93 of yet another embodiment illustrating attachment of the active electrodes of substrate 1 92' over a terminal pin 1 1 4 along with some sort of a weld ring 272 or a braze ring. An electrical connection with weld or solder material 274 is shown.
  • FIGURE 100 illustrates another methodology wherein the lead wire
  • FIGURE 1 01 illustrates a novel laser weld cap 278 with a cut out section 280.
  • the cut out area 280 is formed or cut so the metal cap 278 can slip down over the narrow section 1 92' of the flexible portion of the shielded three-terminal flat-through EMI/energy dissipating filter.
  • 278 can be a stamped titanium, machined titanium, injection molded titanium or a number of other metals.
  • FIGURE 1 02 is a combined cross-section taken generally from 102-
  • the hybrid substrate 1 92 has been modified to accommodate the novel laser weld cap 278 as illustrated in FIG. 1 01 .
  • the laser weld cap 278 is slipped down such that it comes into close contact with the flange 1 20 of the hermetic terminall 1 2.
  • a continuous or discontinuous laser weld or braze 284 is formed as show. This makes a solid metallurgical and low impedance ground contact to the hermetic flange 1 20 and to the laser weld cap 278.
  • FIG. 1 02 An electrical connection 282 is then made to the ground metallization 1 94 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 thereby providing a very low impedance RF ground.
  • ground shield plates 1 94 and 1 94' X' are external for the purposes of this illustration; however, they could be internal plates as previously illustrated.
  • FIGURE 103 is applicable to many of the illustrated embodiments of the present invention and simply illustrates a methodology of having a circuit trace Ti or T2 dodge around a via hole V such that it maintains a high surface area (to maximize ECA) and remains in electrical isolation.
  • circuit trace Ti can be routed in a circular manner all around the via hole or it can simply be routed around the via hole.
  • the upper trace is the preferred embodiment.
  • FIGURE 104 illustrates an alternative embodiment to FIG. 82 in that it is an octapolar design instead of a quadpolar design. Also, instead of having lead wires for transition to integrated circuit boards, it has wire bond pads 286 for convenient connection of jumper wires to other circuits.
  • FIGURE 105 is very similar to FIG. 1 04 except that it illustrates the methodology of breaking up the flex cable portion 1 92' of the hybrid substrate 1 92 into individual arms/traces for direct electrical connection to other locations, for example to an IC board, within a general electronics module or an AIMD.
  • FIGURE 106 illustrates an in-line octapolar hermetic or non- hermetic terminal 1 1 2 with a hybrid substrate 1 92 of the present invention exploded away from it, but designed to be mounted to it.
  • MLCC capacitors 142 that are in series with an embedded inductor meander 1 58.
  • Wire bond pads 1 39 are provided at the end for convenient connection of jumper wires to AIMD or other electronic device electrical circuits.
  • FIGURE 107 is a manufacturing production flow chart illustrating a very low cost and a very reliable way to manufacture the present invention.
  • the particular hybrid substrate 1 92 as previously illustrated in FIG. 84.
  • the first step is to dispense conductive epoxy using a robot to achieve the ring of thermal-setting conductive adhesive 254 as previously described in connection with FIG. 92.
  • This is then assembled into the hermetic seal 1 1 2 and cured at temperatures ranging from 1 50 to 300 degrees centigrade.
  • the electrical chip components are then robot-loaded either from tape and reels or from carrier trays.
  • the chip components can consist of any combination MLCC capacitors 1 42, chip inductors 1 56, diodes 1 54, bandstop filters, L-C trap filters, RFID chips or any other electronic components. These are then run through an automated soldering operation and cleaning operation where they go through an automated optical visual inspection. The electrical inspection is also automated. High reliability screening is then done automatically such as burn in, life testing and the like. Parts are then ready for packaging and shipping.
  • FIGURE 108 illustrates a typical 1 6-lead glass hermetic seal 1 1 2 that would be typically found in a cochlear implant.
  • a novel hybrid substrate 1 92 of the present invention which consists of a rigid section 1 92" and a thin flexible section 1 92'.
  • the thin flexible section 1 92' has been bent over into a 90 degree angle for convenient attachment to the hermetic seal assembly 1 1 2.
  • a number of MLCC capacitors 142 are shown mounted. Not shown are internal ground shield plates of the present invention.
  • the MLCCs 142 can support two purposes in this application. Some of the MLCCs 1 42 are used in series with the flat-through capacitor active electrodes, which are also known in the art as DC blocking capacitors. This is in order to protect body tissues from excessive electrical stimulation.
  • FIG. 109 Referring to the body fluid side of FIG. 109, starting with the top schematic, as we enter into the shielded area Sh, we first encounter the flat- through parasitic capacitances C p that are formed in the present invention between embedded ground shields (not shown) and the particular circuit electrode. We then encounter MLCCA which provides additional low frequency EMI filtering in accordance with the present invention. We then enter MLCCD in series which is a DC blocking capacitor which is placed in series with the circuit trace.
  • FIGURE 1 1 0 illustrates a 5-terminal pin hermetic seal 1 1 2 of the present invention incorporating four quadpolar lead wires 1 1 4-1 1 4'" which are designed to be connected to leads with electrodes that contact body tissue. Also shown is a fifth pin known as the RF antenna pin 288.
  • RF distance telemetry is becoming very popular for AIMDs.
  • telemetry was performed through embedded coils within the AIMD.
  • a close coupled coil was brought up close to the skin over the implant which is also known as a telemetry wand. Signals were sent through this close coupled telemetry field in order to interrogate the implanted medical device, perform reprogramming and the like.
  • a problem with this type of telemetry is that in order to effectively couple RF energy through the skin, it had to be very low in frequency (generally below 200 kHz). Because of the low frequency, the data
  • MLCC capacitors 1 42 connected between the circuit traces and a ground metallization 292.
  • a novel lid assembly 294 which is metallic and is used to provide a shielded compartment which completely encapsulates or encloses the RF telemetry pin antenna 288.
  • the outer termination or shield of the coaxial cable would make electrical and mechanical connection to the ground shield 290.
  • the interior pin of the coaxial cable would enter inside the cavity formed by the lid assembly 294 and make electrical connection to the RF telemetry pin at point 288.
  • FIG. 1 1 1 is an alternative embodiment to the structure of FIG. I l l , wherein reversed geometry MLCC's 142 are used to provide high frequency attenuation. In addition, optional ferrite beads 298 are used to further improve high frequency attenuation.
  • FIGURE 1 1 3 is a manufacturing flow chart that describes an alternative method of manufacturing any of the electronic components of the present invention.
  • Monolithic ceramic capacitor manufacturing is well known in the art. However, a more efficient and cost effective way to do this would be to use thick film technology and lay down the components of the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 all at one time all on one hybrid substrate 1 92.
  • the thick film component is then typically fired in nitrogen at temperatures ranging from 850 to 950 degrees C. This is then laminated into a substrate structure.
  • the layers are printed and etched to form capacitor electrodes and terminations and this is laminated into a substrate or multilayer board and stacked up using prior art application processes. There are then interconnects using conventional vias or micro-vias to complete the fabrication again using all prior art processes.
  • the novel hybrid substrate 1 92 of the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention can also be used to mount a variety of sensing circuits to be used in conjunction with external or lead-based sensors.
  • a number of physiologic sensors could be mounted on the novel substrate, including respiration rate sensors, blood pH sensors, ventricular gradient sensors, cardiac output sensors, pre/post cardiac load sensors, contractility sensors, hemodynamics and pressure monitoring sensors.
  • Such components could also be used in conjunction with blood gas or oxygen sensors.
  • FIGURE 1 1 4 is an outline drawing of an AIMD such as a cardiac pacemaker. Shown is a metallic, typically titanium, housing 300. It is hermetically sealed with a laser weld 302 as shown. It has a hermetic seal 1 1 2, which is also laser welded to the titanium housing 300. The housing is also hermetically sealed by laser weld 302. The hermetic seal 1 1 2 has an insulator 1 1 8, which is well known in the prior art, through which lead wires 1 14-1 14'" pass through in non-conductive relationship with conductive housing 300. A typical pacemaker connector block 304 is shown. This can be in accordance with various international standards organization (ISO) specifications such as IS-I , DF-I , IS-4 and the like.
  • ISO international standards organization
  • the female connector block 304 allows for convenient connection of a lead with a male proximal plug(s), which can be routed to the appropriate body tissue to be sensed or stimulated.
  • the lead wires 1 14 through 1 1 4'" are generally routed to circuit boards, hybrid or integrated circuits or substrates 250 within the active implantable medical device housing 300. These can include cardiac sense circuits, pace circuits and the like.
  • a novel feature is to use the metallic housing of the AIMD as a large surface area energy dissipating surface (EDS). This is also described in U.S. Provisional Patent Application Nos. 61 /1 44,1 02 and 61 /1 49,833, the contents of which are incorporated herein.
  • the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention is an ideal way to reduce to practice and mount all of the various circuit components as described in U.S. Provisional Patent Application Nos. 61 /1 44,102 and 61 /1 49,833.
  • the AIMD is installed in a pectoral pocket, an abdominal pocket or in some other location that is not in intimate contact with a body organ.
  • the housing 300 would be surrounded by fat and muscular tissue which is not nearly as sensitive to thermal damage as, for example, cardiac tissue or brain tissue.
  • the relative surface area of the housing 300 is quite large in comparison to the electrode tip at the end of an implanted lead. In other words, it embodies a great deal of surface area over which to dissipate the MRI RF energy. Accordingly, the thermal rise will be very low (just a few degrees) as opposed to if the energy were concentrated over a small area in electrode tip where the thermal rise can exceed 30 or even 60 degrees centigrade.
  • the housing of the AIMD be used as an energy dissipating surface optionally and ideally working in combination with bandstop filters installed at or near the distal electrode to tissue interface.
  • this energy dissipation is represented by the arrow marked EDS.
  • the energy is being dissipated at all points all around the metallic housing 300 to the surrounding body fluids and tissues.
  • FIGURE 1 1 5 is a close-up view of the variable impedance elements 306 and 308 from FIG. 1 1 4 located within the housing 300 of the AIMD.
  • the variable impedance elements 306 and 308 would be installed on all of the leads that ingress and egress the AIMD.
  • the ground symbol g is shown to indicate that variable impedance element 306 is connected through the shielded ground plates of the three-terminal flat- through EMI/energy dissipating filter of the present invention to the metallic housing 300 of the AIMD.
  • the lead wire lengths are not of particular concern since they will be embedded within the novel shielded three-terminal flat- through EMI/energy dissipating filter technology of the present invention.
  • circuit element 306 would be an MLCC chip 1 42 which would be bonded right at the point of lead wire ingress and egress.
  • FIGURE 1 1 6 illustrates that the variable impedance element 306 of FIG. 1 1 5 can be any type of capacitor (C) element, including MLCC chip capacitors 142 and the like.
  • FIGURE 1 1 7 illustrates that the variable impedance element 306 can also be a feedthrough capacitor C 1 32 as has been noted is in the prior art and illustrated in FIG. 91 .
  • variable frequency selective element 306 can also be an inductor (L) in series with a capacitor (C) also known as a L-C trap filter.
  • FIGURE 1 1 9 illustrates that the trap filter of FIGURE 1 1 8 can be used in combination with either a chip capacitor Cx or equivalent capacitor as previously illustrated in FIGURE 1 1 6 or a feedthrough capacitor as illustrated in FIGURE 1 1 7.
  • Typical capacitance value for the series resonant trap would be 270 nanohenries of inductance and 22 picofarads of capacitance. This would make the series trap filter series resonant at 64 MHz. It's also important that the designer realize that at a certain frequency, the combination of the trap filter 306 and the EMI filter Cx will at some point become a parallel resonant bandstop filter.
  • FIGURE 1 20 is essentially the same as FIGURE 1 1 5 except the focus is now on the series variable impedance element 308.
  • the use of a series impedance element 308 is optional, but highly desirable for AMDs that have sense circuits.
  • variable impedance element 308 can be an inductor L as shown. This forms what is known in the art as a single element low-pass filter.
  • the inductor element L would freely pass low frequencies such as biologic frequencies but would offer a higher impedance to high frequencies such as those of MRI RF pulse frequencies, cellular telephones and the like.
  • FIGURE 1 22 illustrates that the variable impedance element 308 can be a bandstop filter (BSF) consisting of parallel resonant L-C components as shown.
  • BSF bandstop filter
  • FIGURE 1 23 illustrates that the optional series impedance element
  • variable reactance frequency selective element 308 can be any one of a family of low-pass filters. As previously described in connection with FIGURE 1 21 , this could be a single element low-pass filter consisting of a single inductor element L,26 or a single capacitor element C, 20, 306. This could also be an L filter consisting of an inductor element 308, 26, and a second capacitor 304, 20. Variable reactance frequency selective element 308 could also be a T filter or an n element filter which includes ⁇ , LL, five element and the like-type low-pass filters. As one can see from FIGURE 1 23, the attenuation versus frequency slope increases with increasing number of circuit elements.
  • FIGURE 1 24 illustrates a schematic diagram of a series inductor L - capacitor C filter which is commonly known in the industry as an L-C trap filter.
  • the trap filter was previously described in FIG. 1 1 8. Referring once again to FIG. 1 24, there is a particular frequency for a trap filter when the capacitive reactance becomes equal and opposite to the inductive reactance. At this single frequency, the capacitive reactance and the inductive reactance cancel each other out to zero. At this point, all one has left is the parasitic resistance R. If one selects high quality factor (Q) components, meaning that they are very low in resistance, then the trap filter of FIG.
  • Q quality factor
  • FIGURE 1 25 gives the resonant frequency equation where f r , in this case, was measured in hertz. Referring once again to FIG. 1 24, it is very important that the amount of resistance R be controlled. This is better understood by referring to FIGURE 1 26.
  • FIGURE 1 26 is a graph that illustrates the impedance Z in ohms versus frequency of the series resonant L-C trap filter of FIG. 1 24.
  • the impedance is quite high until one reaches the frequency of resonance f r .
  • the impedance of the series L-C trap goes very low (nearly zero ohms).
  • the impedance can be as high as 100 to 1 000 or even 1 0,000 ohms or greater.
  • the impedance tries to go to zero and is limited only be the amount of parasitic resistance R (FIG.
  • the 3 dB bandwidth is preferably selected so that it is convenient to manufacture the filter and tune it to, for example, 64 MHz while at the same time providing a very low impedance R at the resonant frequency.
  • FIGURE 1 27 is an impedance versus frequency curve wherein two trap filters have been installed which are designed to resonate at two different frequencies.
  • the first trap filter consisting of capacitor element C and inductor element L
  • the second trap filter has been installed in parallel consisting of capacitor element C and inductor element L' with component values designed to be self-resonant or have been designed such that the trap filter is self-resonant at 1 28 MHz (the operating frequency of a 3 Tesla MRI system).
  • an optional bandstop filter BSF consisting of the parallel configuration of inductor Lx and capacitor Cx.
  • FIGURE 1 28 is an overall outline drawing showing a cardiac pacemaker 31 0 with endocardial leads implanted into a human heart 31 4 as shown. Each lead is bipolar meaning that it contains two lead wires.
  • lead 31 2 is routed into the right atrium and that lead wire 31 2' is routed into the right ventricular apex (RVA).
  • the distal electrodes for the atrial lead are shown at tip 31 6 and ring electrode 31 8. In the right ventricle, the distal electrode tip 31 6' is shown in close proximity to distal ring electrode 31 8'.
  • bandstop filters in accordance with U.S. Patent No. 7,363,090 would be placed at or near the distal electrodes 31 6, 31 6' 31 8, 31 8' as needed.
  • variable impedance elements 306 and 308 associated with each one of the lead wires which can be incorporated into the shielded three-terminal flat-through EMI/energy dissipating filter 1 90.
  • FIGURE 1 29 is a cross-sectional view of a human head showing a deep brain stimulator electrode 320. Lead wires 31 2 and 31 2' are typically routed down the back of the neck and into the pectoral region and connected to an AIMD (brain neuromodulator).
  • FIG. 1 29 is simply to illustrate that the properties of the present invention are not limited to cardiac pacemakers, but have wide applicability to a wide range of AIMDs as previously described with reference to FIG. 1 .
  • FIG. 1 28 can be integrated into the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention in a housing 320 in the skull burr hole which also supports the deep brain electrodes, or in the AIMD housing as shown in FIG. 1 14.
  • FIGURE 1 30 shows a unipolar lead system 31 2 for an active implantable medical device.
  • a unipolar lead system is shown for simplicity. It will be obvious to those skilled in the art that any number of lead wires 31 2 could be used.
  • this system involves an AIMD and housing 300 attached to unipolar lead wire 31 2 to a human heart 31 4.
  • an optional bandstop filter BSF located at or near the stimulation/sense electrode.
  • the optional bandstop filter BSF located near the distal electrode is more thoroughly described in U.S. Patent 7,363,090 the contents of which are incorporated herein.
  • the implanted lead 31 2 has inductive L and resistive R properties along its length.
  • FIG. 1 30 illustrates the total inductive reactance of lead 31 2 in ohms.
  • the bandstop filter BSF may or may not be present.
  • FIGURE 1 31 illustrates the lead system of FIG. 1 30 wherein an L-C trap filter 306 has been placed inside of housing 300 in a shielded three- terminal flat-through EMI/energy dissipating filter assembly of the present invention.
  • FIGURE 1 32 is another illustration of the unipolar lead system of FIG. 1 30.
  • element 306 features a capacitive element C whose capacitive reactance is given by the equation -j/ ⁇ C.
  • the inductive reactance of the implanted lead would first be calculated (modeled) or measured in ohms. Therefore, the value of capacitance could be selected such that the capacitive reactance -j/ ⁇ C is equal and opposite in ohms to the inductive reactance of the lead +j ⁇ L. In this case, the reactances cancel each other so that one obtains maximal energy transfer to the energy dissipating surface 300,EDS.
  • FIGURE 1 33 is similar to the unipolar lead system previously described in FIGS. 1 30 and 1 32.
  • the capacitance value C has been selected such that the capacitive reactance will be equal and opposite to the inductive reactance of the implanted lead.
  • the resistances are also balanced.
  • the resistance R of the implanted lead is equal in value to a discrete resistor Rx placed inside or outside of the housing 300 of the AIMD.
  • resistor Rx would be incorporated into the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • resistor Rx shall have a finned high surface area housing for maximal heat transfer area to the surrounding encapsulant. Referring once again to FIG. 1 33, one can see that energy is radiated and conducted from a discrete resistance element R x shown as EDS. This energy being dissipated turns to thermal (heat) energy.
  • housing 300 It is desirable to have a relatively large thermal mass located within housing 300.
  • the AIMD housing 300 then becomes a secondary heat dissipating surface (HDS). This thermal energy will be dissipated over the relatively large surface area 300 into body fluids and tissues that surround the AIMD. For example, in a cardiac pacemaker application, housing 300 would be in a pectoral muscle pocket. [Para 319] Referring back to FIGS. 1 32 and 1 33, it is not necessary that the reactances completely cancel, or in the case of FIG. 1 33, it's not particularly important that the resistances are exactly equal. In fact, there is a tradeoff between EMI filtering of the input capacitance and exact cancellation of the +j ⁇ L component lead system.
  • the impedance generally be cancelled in the lead system so that at least the bulk of the excess energy from the MRI RF pulse field will be dissipated to the housing 300 of the AIMD.
  • a 75 picofarad capacitor would exactly cancel the inductive reactance of the lead system
  • the 1 000 picofarad total capacitance (Cp + C) would still draw a large amount of MRI RF energy from the lead system to the housing 300.
  • FIG. 1 34 illustrates filtered connectors 322a-322h that are typically used in the military, aerospace, medical, telecommunication and other industries.
  • an EMI filtered connector such as those typically used in aerospace, military, telecommunications and medical applications, it is very difficult to install a feedthrough capacitor type planar array to the connector housing or back shell without causing excessive mechanical stress to the ceramic capacitor.
  • a number of unique mounting schemes are described in the prior art, which are designs that mechanically isolate the feedthrough capacitor while at the same time provide the proper low impedance ground connection and RF shielding properties. This is important because of the mechanical stresses that are induced in a filtered connector. It is problematic to install a relatively brittle ceramic feedthrough capacitor in a filtered connector because of the resulting mismatch in thermal coefficient of expansion of the surrounding materials, and also the significant axial and radial stresses that occur during connector mating.
  • connectors come in female and male versions to be mated during cable attach.
  • the EMI filtering is typically done in either the female or the male portion, but usually not both.
  • feedthrough capacitors or discrete capacitors in prior art filtered connectors involved very expensive mounting techniques. It is not unusual for the filtered connectors, as illustrated in FIG. 1 34, to cost hundreds or even thousands of dollars each.
  • the present invention using shielded three-terminal flat-through EMI/energy dissipating filter technology offers equal or even higher performance as compared to filtered connector planar array feedthrough capacitors but at a greatly reduced cost and size advantage.
  • FIGS. 1 35 and 1 36 there is shown a prior art sub D-type filtered connector 324 utilizing a planar array feedthrough capacitor (not shown).
  • FIGURES 1 37 and 1 38 illustrate other types of very common connectors.
  • the prior art connectors 326 shown in FIGS. 1 37 and 1 38 are not filtered.
  • FIG. 1 37 one can see the exposed connector pins P. It is very common that these pins that protrude into a shielded housing in connection with the mounting of the connector. As one can see, these pins P can easily be connected to the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
  • FIGURE 1 39 shows a typical connector assembly 330 with an exploded view of a shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention.
  • the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 can take any of the forms described in the present invention.
  • FIGURE 141 is taken generally from partial section 1 41 -1 41 from FIG. 1 39.
  • the shielded three-terminal flat-through EMI/energy dissipating filter embodies an MLCC capacitor C, 306.
  • FIGURE 140 illustrates the connector assembly 330, which can be hermetic or non-hermetic, which has been attached to the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention.
  • the shielded three- terminal flat-through EMI/energy dissipating filters 1 90 of the present invention have broad application and may be used with a wide range of connectors, terminals and/or hermetic seals that support lead wires as they ingress/egress into electronic modules or shielded housings.
  • the flat-through EMI/energy dissipating filters 1 90 of the present invention provide three- terminal capacitive filtering while simultaneously providing shielding of circuits and signals passing through the robust high current capability electrodes of the flat-through capacitor.
  • the hybrid substrate 1 92 forming a major component of the energy-dissipating filter 1 90 of the present invention functions in a very equivalent manner to prior art feedthrough capacitors in that: it's internal ground plates act as a continuous part of the overall electromagnetic shield housing of the electronic device or module to physically block direct entry of high frequency RF energy through the hermetic seal or the equivalent opening for lead wire ingress and egress; and, the flat-through EMI/energy dissipating filter effective shunts undesired high frequency EMI signals off of the lead wire (electrodes) to the overall shield housing where such energy is dissipated in eddy currents resulting in a very small temperature rise.
  • the shielded three-terminal flat-through EMI/energy dissipating filter comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, and a plurality of shield plates substantially enveloping the active electrode plate, wherein the shield plates are collectively coupled to a grounded third terminal. More particularly, the plurality of shield plates include a first shield plate on a first side of the active electrode plate, and a second shield plate on a second side of the active electrode plate opposite the first shield plate. [Para 326] Although several embodiments of the invention have been described in detail for purposes of illustration, various modifications of each may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.

Abstract

A shielded three-terminal flat-through EMI/energy dissipating filter includes an active electrode plate through which a circuit current passes between a first terminal and a second terminal, a first shield plate on a first side of the active electrode plate, and a second shield plate on a second side of the active electrode plate opposite the first shield plate. The first and second shield plates are conductively coupled to a grounded third terminal. In preferred embodiments, the active electrode plate and the shield plates are at least partially disposed with a hybrid flat-through substrate that may include a flex cable section, a rigid cable section, or both.

Description

SHIELDED THREE-TERMINAL FLAT-THROUGH EMI/ENERGY DISSIPATING FILTER
DESCRIPTION
BACKGROUND OF THE INVENTION
[Para 1 ] The present invention relates generally to feedthrough filter capacitor EMI filters. More particularly, the present invention relates to a hybrid EMI filter substrate and/or flex cable assembly which embody embedded shielded flat- through/feedthrough filters and/or energy dissipating circuit elements. This invention is applicable to a wide range of connectors, terminals and/or hermetic seals that support lead wires as they ingress/egress into electronic modules or shielded housings. In particular, the present invention applies to a wide variety of active implantable medical devices (AIMDs). [Para 2] FIGURES 1 -40 provide a background for better understanding the significance and novelty of the present invention.
[Para 3] FIGURE 1 illustrates various types of active implantable and external medical devices 1 00 that are currently in use. FIG. 1 is a wire formed diagram of a generic human body showing a number of implanted medical devices. 1 0OA represents a family of hearing devices which can include the group of cochlear implants, piezoelectric sound bridge transducers and the like. I OOB represents a variety of neurostimulators and brain stimulators. Neurostimulators are used to stimulate the Vagus nerve, for example, to treat epilepsy, obesity and depression. [Para 4] Brain stimulators are pacemaker-like devices and include electrodes implanted deep into the brain for sensing the onset of the seizure and also providing electrical stimulation to brain tissue to prevent the seizure from actually occurring. The lead wires associated with a deep brain stimulator are often placed using real time MRI imaging. Most commonly such lead wires are placed during real time MRI. 10OC shows a cardiac pacemaker which is well- known in the art. 1 0OD includes the family of left ventricular assist devices (LVAD's), and artificial hearts, including the recently introduced artificial heart known as the Abiocor. 1 0OE includes an entire family of drug pumps which can be used for dispensing of insulin, chemotherapy drugs, pain medications and the like. Insulin pumps are evolving from passive devices to ones that have sensors and closed loop systems. That is, real time monitoring of blood sugar levels will occur. These devices tend to be more sensitive to EMI than passive pumps that have no sense circuitry or externally implanted lead wires. 10OF includes a variety of bone growth stimulators for rapid healing of fractures. 1 0OG includes urinary incontinence devices. 1 0OH includes the family of pain relief spinal cord stimulators and anti-tremor stimulators. 10OH also includes an entire family of other types of neurostimulators used to block pain. 1001 includes a family of implantable cardioverter defibrillators (ICD) devices and also includes the family of congestive heart failure devices (CHF). This is also known in the art as cardio resynchronization therapy devices, otherwise known as CRT devices. 1 00J illustrates an externally worn pack. This pack could be an external insulin pump, an external drug pump, an external neurostimulator or even a ventricular assist device. 10OK illustrates the insertion of an external probe or catheter. These probes can be inserted into the femoral artery, for example, or in any other number of locations in the human body. 10OL illustrates one of various types of EKG/ECG external skin electrodes which can be placed at various locations. I OOM are external EEG electrodes placed on the head.
[Para 5] FIGURE 2 is a prior art unipolar discoidal feedthrough capacitor, which has an active internal electrode plate set 102 and a ground electrode plate set 1 04. The inside diameter termination surface 106 is connected electrically to the active electrode plate set 1 02. An outside diameter termination surface 108 is both solderable and electrically conductive, and it is connected to the outside diameter of electrode plate sets 104.
[Para 6] FIGURE 3 is a cross-section of the discoidal feedthrough capacitor of FIG. 2 shown mounted to a hermetic seal 1 1 2 of an active implantable medical device (AIMD). In prior art discoidal feedthrough capacitor devices, the lead wire 1 1 4 is continuous. The hermetic seal 1 1 2 is attached to, typically, a titanium housing 1 1 6, for example, of a cardiac pacemaker. An insulator 1 1 8, like alumina ceramic or glass, is disposed within a ferrule 1 20 and forms a hermetic seal against body fluids. The terminal pin or lead wire 1 14 extends through the hermetic seal 1 1 2, passing through aligned passageways through the insulator 1 1 8 and the capacitor 1 10. A gold braze 1 22 forms a hermetic seal joint between the terminal pin 1 14 and the insulator 1 1 8. Another gold braze 1 24 forms a hermetic seal joint between the alumina insulator 1 1 8 and the titanium ferrule 1 20. A laser weld 1 26 provides a hermetic seal joint between the ferrule 1 20 and the housing 1 1 6. The feedthrough capacitor 1 10 is shown surface mounted in accordance with U.S. Patent 5,333,095, and has an electrical connection 1 28 between its inside diameter metallization 1 06 and hence the active electrode plate set 102 and lead wire 1 1 4. There is also an outside diameter electrical connection 1 30 which connects the capacitor's outside diameter metallization 108 and hence the ground electrodes 1 04 to the ferrule 1 20. Feedthrough capacitors are very efficient high frequency devices that have minimal series inductance. This allows them to operate as EMI filters over very broad frequency ranges. Referring once again to FIG. 3, one can see that another way to describe a prior art discoidal feedthrough capacitor 1 1 0 is as a three-terminal capacitor. Three-terminal devices generally act as transmission lines. Referring to FIG. 3, one can see that there is a current "i" that passes into lead wire 1 1 4. For a prior art AIMD, on the body fluid side there is generally an implanted lead which can undesirably act as an antenna which can pick up energy from environmental emitters. This energy is known as electromagnetic interference (EMI). Cell phones, microwave ovens and the like have all been implicated in causing interference with active implantable medical devices. If this interference enters lead wire 1 1 4 at point X (FIG.3), it is attenuated along its length by the feedthrough capacitor 1 1 0. Upon exiting, the undesirable high frequency EMI has been cleaned off of the normal low frequency circuit current (such as pacemaker pacing pulses or biologic frequency sensors) so that the high frequency EMI has been significantly attenuated. Another way of looking at this is as the high frequency energy passes from terminal 1 to terminal 2 (FIGS. 3 and 4), it is diverted through the feedthrough capacitor 1 1 0 to the ground terminal which is also known as the third terminal or terminal 3. The feedthrough capacitor 1 1 0 also performs a two other important functions: a) its internal ground electrodes 1 02 and 1 04 act as a continuous part of the overall electromagnetic shield housing of the electronic device or module which physically blocks direct entry of high frequency RF energy through the hermetic seal 1 1 2 or equivalent opening for lead wire ingress and egress in the otherwise completely shielded housing (such RF energy, if it does penetrate inside the shielded housing can couple to and interfere with sensitive electronic circuitry), and; b) the feedthrough capacitor 1 10 very effectively shunts undesired high frequency EMI signals off of the lead wires to the overall shield housing where such energy is dissipated in eddy currents resulting in a very small temperature rise. [Para 7] FIGURE 4 is a schematic diagram showing the discoidal feedthrough capacitor 1 10 previously described in connection with FIGS. 2 and 3. As one can see, it is a three-terminal device consistent with terminals 1 , 2 and 3 illustrated in FIG. 3.
[Para 8] FIGURE 5 is a quadpolar prior art feedthrough capacitor 1 32 which is similar in construction to that previously described in FIG. 2 except that it has four through holes.
[Para 9] Throughout this description, functionally equivalent elements will be given the same reference number, irrespective of the embodiment being shown. [Para 10] FIGURE 6 is a cross-section showing the internal electrodes 1 02, 104 of the capacitor 1 32 of FIG. 5.
[Para 1 1 ] FIGURE 7 is a schematic diagram showing the four discrete feedthrough capacitors comprising the quadpolar feedthrough capacitor 1 32 of
FIGS. 5 and 6.
[Para 12] FIGURE 8 is an exploded electrode view showing the inner and outer diameter electrodes of the unipolar feedthrough capacitor 1 10 of FIGS. 2 and 3. One can see the active electrode plates set 1 02 and the ground electrode plate set 104. Cover layers 1 34 are put on the top and bottom for added electrical installation and mechanical strength.
[Para 1 3] FIGURE 9 is an exploded view of the interior electrodes of the prior art quadpolar feedthrough capacitor 1 32 previously illustrated in FIG. 5. As shown in FIG. 9, the active electrode plate sets are shown as 1 02 and the ground electrode plates are shown as 104. Cover layers 1 34 serve the same purpose as previously described in connection with FIG. 8.
[Para 14] FIGURE 10 illustrates a prior art quadpolar feedthrough capacitor
1 32 mounted on top of a hermetic insulator 1 1 8 wherein a wire bond substrate
1 36 is attached to the top as shown. Wire bond pads 1 38, 1 38', 1 38", 1 38'" and 1 40 are shown for convenient connection to the internal circuitry of the
AIMD. This is more thoroughly described in FIGS. 75 and 76 of U.S. Patents
7,038,900 and 7,31 0,21 6, the contents of which are incorporated herein.
[Para 1 5] FIGURE 1 1 is a cross-section taken generally from section 1 1 -1 1 from FIG. 10. In FIG. 1 1 , the internal circuit traces Ti through T4 to the wire bond pads 1 38-1 38'" are shown. Referring back to FIG. 10, there is an additional wire bond pad 1 40 shown on the left side of the wire bond substrate 1 36. This is also shown in FIG. 1 1 . This is a ground connection to the outside diameter of the hermetic seal ferrule 1 20 and provides a convenient connection point for electronic circuits and the like that need a ground attachment point on the inside of the AIMD.
[Para 16] FIGURE 1 2 is a schematic diagram of the prior art wire bond pad quadpolar hermetic feedthrough 1 32 of FIG. 1 0.
[Para 1 7] FIGURE 1 3 is a prior art monolithic ceramic capacitor (MLCC) 142. These are made by the hundreds of millions per day to service the consumer electronics and other markets. Virtually all cell phones and other types of electronic devices have many of these. In FIG. 1 3, one can see that the MLCC 1 42 has a body 144 generally consisting of a high dielectric constant ceramic such as barium titinate. It also has solderable termination surfaces 1 46 and 1 48 at either end. These termination surfaces 1 46 and 1 48 provide a convenient way to make a connection to the internal electrode plates of the MLCC capacitor 142. FIG. 1 3 can also take the shape and characteristics of a number of other types of capacitor technologies, including rectangular, cylindrical, round, tantalum, aluminum electrolytic, stacked film or any other type of capacitor technology.
[Para 18] FIGURE 14 is a sectional view taken from section 1 4-1 4 in FIG. 1 3. The left hand electrode plate set is shown as 1 50 and the right hand electrode plate set is shown as 1 52. One can see that the left hand electrode plates 1 50 are electrically connected to the external metallization surface 146. The opposite electrode plate set (or right hand plate set) 1 52 is shown connected to the external metallization surface 148. One can see that prior art MLCC and equivalent chip capacitors are also known as two-terminal capacitors. That is, there are only two ways electrical energy can connect to the body of the capacitor. In FIGS. 1 3 and 1 4, the first terminal "1 " is on the left side and the second terminal "2" is on the right side.
[Para 19] FIGURE 1 5 is an ideal schematic diagram of the prior art MLCC capacitor 1 42 of FIG. 1 3.
[Para 20] FIGURE 1 6 is a more realistic schematic diagram showing the fact that the MLCC 1 42 structure as illustrated in FIG. 1 3 has series inductance L. This inductive property arises from the fact that it is a two-terminal device and does not act as a transmission line. That is, its lead wires and associated internal electrodes all tend to add series inductance to the capacitor. It is well known to electrical engineers that MLCC capacitors will self-resonate at a particular frequency. FIGURE 1 7 gives the formula for this resonant frequency. There is always a point at which the capacitive reactance as shown in FIG. 1 6 is equal and opposite to the inductive reactance. It is this point that these two imaginary components cancel each other out. If it weren't for resistive losses, at the resonant frequency the impedance between 1 46,1 and 148,2 as shown in FIG. 1 6 would go to zero. However, the resistive losses of the inductor L and the equivalent series resistance of the capacitor C prevent this from happening. This is better understood by referring to FIGURE 1 8. [Para 21 ] Shown in FIG. 1 8 are three curves. An ideal capacitor curve is shown which is very similar to the response of a feedthrough capacitor, such as shown in FIG. 3. One can see that the attenuation goes up fairly linearly with frequency all the way up to very high frequencies even above 10,000 MHz. The MLCC curve is for the capacitor of FIG. 1 3. At low frequencies, in this case below 1 00 MHz, the MLCC curve tracks very closely to an ideal or a feedthrough capacitor. However, as the MLCC nears its self-resonant frequency (SRF), its attenuation tends to go up dramatically. This is because when one refers back to FIG. 1 6, the inductive and capacitive reactance elements are tending to cancel each other out. As previously mentioned, if it weren't for its resistive losses at resonance (SRF), the MLCC chip would look like a short circuit, in which ideal case its attenuation would be infinite. This means that if it weren't for these resistive losses, we would have infinite attenuation at the SRF. Instead what we have is a peak of approximately 60 dB as shown. Above resonance, the MLCC capacitor becomes increasingly inductive and the attenuation drops dramatically. This is an undesirable effect and this is why feedthrough capacitors have generally been the preferred choice for use in EMI broadband filters.
[Para 22] FIGURE 1 9 shows three different size MLCC capacitors Ci - C3 connected around a unipolar feedthrough pin or lead wire 1 14. Self-resonant frequency is dependent upon the internal inductance of a capacitor. This was illustrated and described in connection with FIG. 1 6. One can reduce the amount of inductance by using a physically smaller MLCC capacitor. For example, referring to FIG. 1 9, one could have one each of what is known in the art as a size 0402, a 0603 and a 0805 MLCC capacitor. This is an EIA designation wherein, for example, 0805 would be 0.080 inches long and 0.050 inches wide. Accordingly, these three MLCC capacitors C1-C3 would have three different resonant frequencies. This is more thoroughly described in U.S. Patent 5,973,907 and U.S. Patent 5,959,336 the contents of which are incorporated herein by reference. Figure 20 is the schematic diagram for the three MLCC capacitors of FIG. 1 9.
[Para 23] FIGURE 21 shows the attenuation response for the three chip capacitor unipolar hermetic terminal in FIG. 1 9. These three capacitors Ci - C3 are acting in parallel as shown in the schematic diagram of FIGURE 20. Referring to FIG. 21 , we can see that there are now three resonant peaks representing the self-resonant frequency of each of these individual MLCC capacitors acting together in parallel. Shown for reference is the ideal capacitor response curve previously shown in FIG. 1 8. The SRF for Ci , C2 and C3 are also shown. The physically largest capacitor Ci will have the lowest self-resonant frequency whereas the physically smaller capacitor (C3) will have the highest self-resonant frequency. This is because, in general, the smaller the MLCC capacitor, the lower its internal inductance. Secondary factors that determine the value of the undesirable equivalent series inductance (ESL) of an MLCC capacitor include the number and spacing of internal electrodes, geometry, form factor and circuit board mounting techniques. [Para 24] Referring once again to FIG. 1 9, the reason why this approach has never been commonly practiced in the AIMD market is the fact that this is a complicated design and is also costly. Because of the space limitations and reliability implications, packing this many components into such a small place becomes impractical.
[Para 25] FIGURE 22 shows a different method of mounting MLCC capacitors, for example, those previously shown in FIG. 1 9. In the industry, this is known as the tombstone mounting position, which is a highly undesirable thing to do when the capacitor is to be used as an EMI filter or an RF decoupling device (bad mounting and bad form factor). This is because the capacitor's inductive loop area Li tends to increase. The increased inductive loop area (integral of area bounded under the loop) has the effect of directly raising the inductance L as previously described in connection with FIG. 1 6. The reason this is undesirable is this particular capacitor will tend to self-resonate at a much lower frequency (and thereby becomes a less effective high frequency device or EMI filter).
[Para 26] FIGURE 23 illustrates a more desirable way to mount the MLCC capacitor 1 42 of FIG. 22. This is a conventional flat surface mount technique, which has a much lower inductive loop area L2 as shown (area bounded under the loop). Accordingly, even though the two capacitors are identical in size and capacitance value, the MLCC capacitor 1 42 as shown in FIG. 23 will resonate at a much higher frequency before it starts to become undesirably inductive. [Para 27] FIGURE 24 is known in the art as a reverse geometry MLCC capacitor 1 42'. For comparative purposes, the physical size of the MLCC capacitor illustrated in FIG. 24 is exactly the same dimensions as the MLCC capacitors 142 previously shown in FIGS. 22 and 23. The important thing is the location of the termination surfaces 146' and 148'. The MLCC capacitor 1 42' in FIG. 24 has been terminated along its long sides. Accordingly, its inductive loop area or the area bounded underneath the loop L3 is the smallest of all the loop configurations. Thus, the capacitor 142' of FIG. 24 will self-resonate at a much higher frequency as compared to the MLCC capacitors 1 42 shown in FIGS. 22 and 23. A good treatment of this is found in a technical paper entitled, A CAPACITOR'S INDUCTANCE, which was given at the Capacitor and Resistor Technology Symposium in Lisbon, Portugal, October 1 9-22, 1 999. This paper was co-authored by Robert Stevenson and Dr. Gary Ewell of Aerospace Corporation. A related paper was given entitled, A CAPACITOR'S INDUCTANCE: CRITICAL PROPERTY FOR CERTAIN APPLICATIONS and was given by the same authors at the 49th Electronic and Components Technology Conference of the Institute of Electrical and Electronic Engineers held June 1 -4,1 999 in San Diego, California.
[Para 28] FIGURE 25 is the same electrical schematic diagram as previously illustrated in FIG. 1 6, but additionally showing the equivalent circuit model for an MLCC. Added are resistors IR and ESR. IR is the insulation resistance of the capacitor C. For electronic circuit analysis reasons, this IR resistor can generally be ignored. The reason for this is that it is typical that the value of IR is in excess of 1 0 Gigaohms (10,000,000,000 ohms). This number is so high compared to the values of the other components of the capacitor circuit model that it can be safely ignored. Also added to the complete schematic model shown in FIG. 25 is the capacitor series resistance (ESR). This is the total ESR including the dielectric loss tangent of the ceramic materials themselves and all ohmic losses and other electrical connections within and external to the capacitor itself. As previously stated, the presence of resistor ESR is why at the self-resonant frequency, the insertion loss does not go to infinity. [Para 29] FIGURE 26 is a prior art chip transient suppression diode 1 54, such as a Transorbtm or the like.
[Para 30] FIGURE 27 is a schematic diagram showing the diode chip 1 54 of FIG. 26 connected between an active medical device lead wire 1 1 4 and circuit ground. The dashed line shown in FIG. 27 illustrates the shielded housing of the AIMD. The reason for diode chip 1 54 (or multiple diode arrays) is to help protect the sensitive electronic circuits of the AIMD from external high voltage insults. These could be electrostatic discharges or the application to the patient of automatic (high voltage) external defibrillation (AED). AEDs are commonly now found in government buildings, airports, airplanes and the like. It is very important that a pacemaker not be burned out during the application of an AED external defibrillation event. The diode chip 1 54 shown in FIGS. 26 and 27 basically is typically an avalanche type diode which is also known in the art as a zener diode. In other words, they do not forward bias or short out until a certain voltage threshold is reached. These are also known in the art as Transorbs™ and also have other market names. Such diodes can be back to back and placed in parallel in order to suppress biphasic high voltage AED defibrillation pulses.
[Para 31 ] FIGURE 28 is a prior art inductor chip 1 56. There are many manufacturers of these. These can either have ferrite elements or be non- ferromagnetic. They come in a variety of size's inductance values and voltage ratings.
[Para 32] FIGURE 29 is a schematic diagram of the inductor chip 1 56 of FIG. 28.
[Para 33] Referring to FIGURE 30, one can see that an inductor circuit trace 1 58 is printed or deposited right on top of a prior art MLCC capacitor 1 42 to form an MLCC-T 1 60. The advantage here is that low cost MLCCs which have been produced from very high volume commercial capacitor operations could be utilized and the inductor trace 1 58 could be printed on as a supplemental operation. This forms a parallel inductor (L) - capacitor (C) resonant L-C circuit which creates a very high impedance at its resonant frequency. This is effective for suppressing a single RF frequency, such as that from magnetic Resonance Imaging (MRI) equipment, or the like. This is more thoroughly described in U.S. Patent Application Publication No. US 2007-01 1 2398 Al , the contents of which are incorporated herein by reference.
[Para 34] FIGURE 31 shows yet another way to deposit an inductor shape 1 58 onto a separate substrate 1 62 to form a parallel L-C resonant circuit. For example, the substrate 1 62 could be of alumina ceramic or other suitable circuit board material. This could then be bonded with a thin adhesive layer 1 64 to a prior art MLCC capacitor 1 42. The composite MLCC-T structure 1 60', including corresponding metallization surfaces 146 and 1 48 on opposite ends, is illustrated in the electrical schematic diagram of FIGURE 34 where it is evident that the structure forms a parallel L and C "tank" or bandstop circuit. [Para 35] FIGURE 32 is an isometric view of a novel composite monolithic ceramic capacitor-parallel resonant tank (MLCC-T) 1 60" which forms a bandstop or tank filter 1 66 in accordance with previously referenced U.S. Patent Application Serial Number 1 1 /558349. Viewed externally, one can see no difference between the MLCC-T 1 60" of the present invention and prior art MLCC capacitor 142 as shown in FIG. 1 3. However, the novel MLCC-T 1 60" has an embedded inductor 1 62 which is connected in parallel across the capacitor between its opposite termination surfaces 1 46 and 148. [Para 36] FIGURE 33 illustrates an exploded view of the various layers of the novel MLCC-T tank filter 1 60" shown in FIG. 32. The novel MLCC tank (MLCC- T) 1 60" includes an embedded inductor 1 62. At low frequencies, the embedded inductor 1 62 shorts out the capacitor from one end to the other. However, at high frequency, this forms a parallel tank circuit 1 66 which is again better understood by referring to the schematic diagram in FIGURE 34. Referring once again to FIG. 33, one can see that as the capacitor stacks up from the top, we have an area of blank cover sheets 1 68 followed by one or more embedded inductor layers 1 62. These inductor traces can have a variety of shapes as further illustrated in FIGURE 83 of U.S. Patent Application Publication No. US 2007-01 1 2398 Al . It will be obvious to those skilled in the art that there are a variety of optional shapes that could also be used. Then there are a number of other blank interleafs 1 70 before one gets to the capacitor electrode plate sets, 1 50 and 1 52. One can see the capacitor electrode plate set 1 50 which connects to the left hand termination 146 and one can also see the capacitor electrode plate set 1 52 which connects to the right hand termination 1 48. In FIG. 33, only single electrodes are shown as 1 50, 1 52. However, it will be obvious to those skilled in the art that any number of plates "n" could be stacked up to form the capacitance value that is desired. Then bottom blank cover sheets 1 68 are added to provide insulative and mechanical strength to the overall TANK filter MLCC-T 1 60". [Para 37] After sintering the composite structure at high temperature, the last step, referring back to FIG. 32, is the application of the solderable termination surfaces 146 and 1 48. These termination surfaces can be a thick film ink, such as palladium silver, glass frit, a gold plating, or the like and applied in many processes that are known in the art. Once again, the overall MLCC-T 1 60", which is illustrated in FIG. 32, looks identical to a prior art MLCC 1 42 as shown in FIG. 1 3. However, embedded within it is a novel parallel inductor structure 1 62 creating a novel parallel tank or bandstop filter 1 66 shown in the schematic diagram of FIG. 34.
[Para 38] Referring to schematic drawing FIG. 34, one can see that the inductor L has been placed in parallel with the capacitor C which is all conveniently located within the monolithic structure MLCC-T 1 60" shown in FIG. 32.
[Para 39] In FIG. 35 only one pole of a quadpolar feedthrough capacitor 1 32 is shown, which is better understood by referring to its schematic diagram shown in FIG. 36. One can see that there is a feedthrough capacitor 1 1 0 which is also known as a broadband EMI filter shown as Ci , C2, C3 and C4 in FIG. 36. In line with each one of these circuits is a parallel resonant bandstop filter MLCC-T 1 60 to block MRI pulsed RF frequencies or frequencies from similar powerful emitters. The function of these bandstop filters is better understood by referring to the complete description in U.S. Patent No. 7,363,090, the contents of which are incorporated herein.
[Para 40] Referring once again to FIG. 35, one can see that there is a metallic ferrule 1 20 which is attached to a hermetic insulator 1 1 8 by means of gold braze 1 24. There are also two lead wires 1 1 4 and 1 14' as shown. Lead wire 1 14 is mechanically and hermetically attached to insulator 1 1 8 by means of gold braze material 1 22. The bandstop filter or tank filter MLCC-T 1 60 is held in place with an insulative spacer plate 1 72. The feedthrough capacitor 1 32 is mounted on top as shown. Lead wire 1 14' is attached to the other end of the tank filter MLCC-T 1 60. A capacitor outside diameter metallization 108 connects to the capacitor's internal ground electrodes 1 04. Electrical connection 1 30 is made between the capacitor's outside diameter metallization 1 08 and both the metal of the ferrule 1 20 and gold braze material 1 24. [Para 41 ] FIGURE 37 is a different type of prior art MLCC feedthrough capacitor 1 42 that is built into a special configuration. It is known in the art by some as a flat-through capacitor (it also has other trade names). It will be referred to herein as a flat-through capacitor 1 74. At low frequencies, the flat- through capacitor 1 74 exhibits ideal capacitance behavior versus frequency. That is, its attenuation curve versus frequency is nearly ideal. This is because it is truly a three-terminal device which acts as a transmission line in a manner similar to those of prior art discoidal feedthrough capacitors 1 1 0. This is better understood by referring to its internal electrode plate geometry as shown in FIGURE 38. Shown is a through or active electrode plate 1 76 that is sandwiched between two ground electrode plates 1 78. The through or active electrode plate 1 75 is connected at both ends by termination surfaces 1 80 and 1 82. When the capacitor is mounted between circuit trace lands 1 84 and 1 86 as shown in FIG. 37, this connects the circuit trace together between points 1 84 and 1 86. Referring to the active circuit trace 1 75 in FIG. 38, one can see that there is a current /ι that enters. If this is a high frequency EMI current, it will be attenuated along its length by the capacitance of the flat-through capacitor and emerge as a much small in amplitude EMI signal at terminal 2 as /V. Similar to discoidal feedthrough capacitors, the flat-through capacitor 1 74 is also a three-terminal capacitor as illustrated in FIG. 37. The point of current input /l is terminal 1 , the point of circuit current egress /ϊ ' is known as terminal 2 and ground is known as terminal 3. In other words, any RF currents that are flowing down the circuit trace must pass through the electrodes 1 75 of the capacitor 1 74. This means that any RF signals are exposed for the full length of the electrode plate 1 75 between the ground electrodes 1 78 and the capacitance that is formed between them. This has the effect of making a very novel shape for a three-terminal feedthrough capacitor. One negative to this type of capacitor 1 74 is that it is not conveniently mountable in such a way that it becomes an integral part of an overall shield. There is always a frequency at which undesirable RF coupling 1 88 across the device will occur. This usually does not happen until 100 MHz or above. At very high frequencies, such as above 1 GHz, this problem becomes quite serious. Another negative, as compared to prior art discoidal feedthrough capacitors 1 10 (where the circuit current passes through a robust lead in a feedthrough hole), is that the flat- through capacitor circuit currents must flow through the electrodes of the flat- through capacitor itself (in prior art discoidal/feedthrough capacitors, the only current that flows in the electrodes is high frequency EMI currents). Monolithic ceramic manufacturing limitations on electrode thickness and conductivity means that prior art flat-through capacitors 1 74 have relatively high series resistance and can only be rated to a few hundred milliamps or a few amps at best (however, an implantable defibrillator must deliver a high voltage pulse of over 20-amps). Prior art MLCC and flat-through electrodes must be kept relatively thin to promote ceramic grain growth through the electrodes in order to keep the capacitor layers from delaminating during manufacturing or worse yet, during subsequent mechanical or thermal shocks which can cause latent failures. [Para 42] FIGURE 39 is the schematic diagram of the prior art flat-through capacitor 1 74 as illustrated in FIG. 37. Note that its schematic diagram is the same as that for the feedthrough capacitor 1 1 0 shown in FIGS. 2 and 3. The difference is that feedthrough capacitors are inherently configured to be mounted as an integral part of an overall shield which precludes the problem of RF coupling (see FIGS. 5-7).
[Para 43] FIGURE 40 illustrates the attenuation versus frequency response curve which is shown generically for the flat-through capacitor of FIG. 37. If it weren't for cross-coupling of RF energy, it would perform as an ideal or nearly perfect capacitor would. However, because of this cross-coupling, there is always going to be a certain frequency at which the attenuation starts to parasitically drop off as shown. This drop off is very undesirable in active implantable medical device (AIMD) applications in that there would be less protection against high frequency EMI emitters such as cellular phones and the like. This parasitic drop off in attenuation due to cross-coupling is even a worse problem in military and space applications where EMI filter attenuation requirements of up to 10 or even 1 8 GHz, is important (implantable medical applications don't generally require filtering much above 3 GHz due to the effective reflection and absorption of human skin of RF energy at frequencies above 3 GHz). Space and military circuits have to operate in the presence of extremely high frequency emitters, such as GHz radars and the like. Accordingly, there is a need for a flat-through type of capacitor that eliminates the problems associated with this parasitic attenuation degradation due to RF cross-coupling across (or outside of around) the capacitor. In addition, there is also a need for flat-through capacitors that can handle much higher circuits through their "through" electrodes. The present invention fulfills these needs and provides other related advantages.
SUMMARY OF THE INVENTION
[Para 44] A primary object of the present invention is to provide a novel shielded three-terminal flat-through EMI/energy dissipating filter which embodies one or more flat-through capacitors whose internal electrodes are high frequency shielded, are much thicker (compared to prior art MLCC flat- through thick film electrode technology) and higher in both cross-sectional and surface area (robust and able to carry much higher through circuit currents), whose electrodes can be configured with integral co-planar inductor elements, and can be optionally configured to accept a variety of surface mounted electronic components (like additional discrete or embedded capacitors, inductors, diodes, RFID chips, and the like). The higher surface area of the novel shielded three-terminal flat-through EMI/energy dissipating filter of the present invention maximizes the value of the flat-through capacitance. The present invention resides in a shielded three-terminal flat-through EMI/energy dissipating filter which comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, and a plurality of shield plates substantially enveloping the active electrode plate, wherein the shield plates are conductively coupled to a grounded third terminal. Preferably, the plurality of shield plates include a first shield plate on a first side of the active electrode plate, and a second shield plate on a second side of the active electrode plate opposite the first shield plate. The active electrode plate is insulated from the shield plates by a dielectric material such that the active electrode plate and the shield plates cooperatively form a flat-through capacitor. A lead wire typically extends through at least one of the shield plates in non-conductive relation. The lead wire is conductively coupled to the active electrode plate to form the first terminal. A shielded fixture may be provided through which the lead wire extends in non- conductive relation. The fixture may comprise an hermetic seal for, for example, an active implantable medical device (AIMP). The surface area of the active electrode plate is maximized to increase parasitic capacitance and minimize resistance to current flow.
[Para 45] In some embodiments, a plurality of active electrode plates are provide which each have a first shield plate on a first side thereof and a second shield plate on a second side thereof opposite the first shield plate. Each active electrode plate is insulated from its adjacent shield plates by a dielectric material such that each active electrode plate and its adjacent shield plates cooperatively form a flat-through capacitor. The shield plates are conductively coupled to a common ground. A plurality of lead wires are provided which each extends through at least one of the shield plates in non-conductive relation. Each lead wire is conductively coupled to a respective active electrode plate to form the first terminal for said active electrode plate. [Para 46] The shielded three-terminal flat-through EMI/energy dissipating filter may further include an adjacent feedthrough capacitor through which the lead wire extends prior to conductively coupling to the active electrode plate to form the first terminal.
[Para 47] A conductive pad may be conductively coupled to the active electrode plate to form the second terminal. The conductive pad may comprise a wire bond pad disposed on an exterior surface of a body of dielectric material through which the active electrode plate extends.
[Para 48] The shielded three-terminal flat-through EMI/energy dissipating filter may include a plurality of co-planar active electrode plates insulated from the shield plates by a dielectric material such that each active electrode plate and the shield plates cooperatively form a flat-through capacitor. Moreover, at least one of the co-planar active electrode plates may comprise an inductor. In several illustrated embodiments, a co-planar third shield plate extends between the co-planar active electrode plates.
[Para 49] In various embodiments, a lead wire or pin extends through at least one of the shield plates in non-conductive relation, wherein the lead wire or pin conductively couples to the active electrode plate to form the second terminal. A monolithic chip capacitor (MLCC) may be conductively coupled between the active electrode plate and at least one of the grounded shield plates. Further, a third shield plate may be disposed generally co-planarly with the active electrode plate, wherein the third shield plate is conductively coupled to the grounded third terminal. The third shield plate may substantially surround the active electrode plate and be disposed between the first and second shield plates.
[Para 50] The shielded three-terminal flat-through EMI/energy dissipating filter may further be modified such that at least a portion of the active electrode plate comprises an inductor. The inductor may comprise a spiral circuit trace. [Para 51 ] In various embodiments of the EMI/energy dissipating filter, at least one via hole is provided for conductively coupling the shield plates to one another. The via holes may be disposed about the periphery of the active electrode plate to enhance its shielding characteristics. [Para 52] In various embodiments, the active electrode plate may be configured to form at least a component of an "L", "π", "T", "LL", "5 element" or an "n" element passive electronic low pass filter. Moreover, the active electrode plate may be configured to form at least a component of a band stop filter, a diode array, or an RFID chip. When used in connection with an active implantable medical device, the shielded three-terminal flat-through EMI/energy dissipating filter utilizes passive electronic device components which are optimized for use at MRI frequencies.
[Para 53] In some embodiments, the active electrode plate and the first and second shield plates are disposed generally perpendicularly to a lead wire conductively coupled to the active electrode plate to form the first terminal. In another embodiment, the active electrode plate and the first and second shield plates are disposed generally parallel to a lead wire conductively coupled to the active electrode plate to form the first terminal. [Para 54] The active electrode plate and the shield plates are typically at least partially disposed within a hybrid flat-through substrate. This hybrid flat- through substrate may include surface metallization forming the third terminal. In many of the illustrated embodiments, the hybrid flat-through substrate is disposed adjacent to a hermetic seal for an implantable medical device such that the surface metallization is conductively coupled to a housing for the implantable medical device through a conductive ferrule of the hermetic seal. [Para 55] The hybrid flat-through substrate may comprise a flex cable section, a rigid section, or a composite of both types. The flex cable section may comprise a polyimide, Kapton or acrylic material. The rigid section may comprise a high dielectric constant ceramic, alumina, fiberglass or FR4 material.
[Para 56] The rigid section of the hybrid substrate may include at least one passive electronic component conductively coupled to the active electrode plate. The passive electronic component may comprise an RFID chip, a capacitor, an inductor, a band stop filter, an L-C trap filter, a diode, or a diode array. The capacitor typically comprises a monolithic chip capacitor, and the inductor typically comprises a monolithic chip inductor or a toroidal inductor. [Para 57] The second terminal of the active electrode plate may be conductively coupled to a circuit board for an electronic device, such as the internal circuit board of an AIMD.
[Para 58] In another embodiment, the hybrid flat-through substrate comprises a dielectric material with the active electrode plate embedded therein. The active electrode plate is conductively coupled to surface metallization for at least one via hole through the substrate. The shield plates comprise surface metallization applied to exterior surfaces of the hybrid flat- through substrate. A conductive cap may be provided which is configured to capture the hybrid flat-through substrate and conductively couple the shield plates to a ground. Such structure may be utilized in connection with a hermetic seal for an implantable medical device. The hermetic seal would typically include a conductive ferrule to which the conductive cap is conductively attached, at least one lead wire extending through the ferrule in non-conductive relation and conductively coupled to the surface metallization of the via hole
[Para 59] The shielded three-terminal flat-through EMI/energy dissipating filter may be constructed such that all external components thereof comprise biocompatible materials designed for direct body fluid exposure. Moreover, the aforementioned RFID chips may include a wake-up feature for initializing AIMD RF telemetry circuits.
[Para 60] The aforementioned shielded three-terminal flat-through EMI/energy dissipating filters may be incorporated into a passive component network for an implantable lead of an active implantable device (AIMD). The passive component network comprises at least one lead wire having a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at a distal end, an energy dissipative surface disposed adjacent to tissue or within the blood or lymph flow of a patient at a point distant from the electrode, and a diversion circuit associated with the lead wire, for selectively diverting high-frequency energy away from the electrode to said energy dissipative surface for dissipation of said high frequency energy as heat. The passive component network may include an impeding circuit associated with the diversion circuit for raising the high frequency impedance of the lead wire. The impeding circuit is typically disposed between said diversion circuit and the distal end of said at least one lead wire, and typically comprises an inductor or a band stop filter.
[Para 61 ] The at least one lead wire may comprise a portion of a probe or a catheter. Moreover, the energy dissipative surface may comprise a sheath, an insulative body, or a thermally conductive element. Moreover, the at least one lead wire may comprise at least a pair of lead wires each having a length extending between and to a proximal end and a tissue stimulating or biological-sensing electrode at a distal end. The diversion circuit couples each of said lead wires to said energy dissipative surface. The diversion circuit may further be coupled between the pair of lead wires. [Para 62] The high frequency energy typically comprises an RF post frequency of a magnetic resonance scanner in a preferred embodiment. The high frequency energy may further comprise a range of selected RF pulsed frequencies.
[Para 63] The diversion circuit may comprise a low pass filter including at least one of a C filter, and L filter, a T filter, a Pl (π) filter, an LL filter, a 5- element filter, or an "n" element filter. The diversion circuit may further comprise at least one series resonant L-C trap filter. Moreover, the impeding circuit may include a non-linear circuit element. In this case, the non-linear circuit element may comprise a diode or a transient voltage suppressor. In various embodiments, the diversion circuit may comprise at least one series resonant L-C trap filter, and wherein the impeding circuit comprises an inductor or a band stop filter.
[Para 64] It will be appreciated that the basic point of novelty of the three- terminal flat-through EMI/energy dissipating filter is that it comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, a first shield plate on a first side of the active electrode plate, and second shield plate on a second side of the active electrode plate opposite the first shield plate, wherein the first and second shield plates are conductively coupled to a grounded third terminal. The effective capacitance area or overlapping surface area of the active electrode plate and its surrounding grounded shield plates have been relatively maximized in order to achieve a higher value of capacitance of the three-terminal flat-through capacitor. The dielectric constant of the insulating layers between the active electrode plate and the surrounding ground shied plates have also been substantially raised in order to achieve a higher capacitance value for the three- terminal flat-through capacitor. Preferably, the dielectric thickness separating the active electrode plate and the surrounding ground shield plate is relatively minimized in order to achieve a higher capacitance value. A number of redundant parallel layers of the active electrode plate and surrounding grounded shield plates are provided to increase the total capacitance value of the three-terminal flat-through capacitor.
[Para 65] Other features and advantages of the present invention will become apparent from the following more detailed description, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[Para 66] The accompanying drawings illustrate the invention. In such drawings:
[Para 67] FIGURE 1 is a wire formed diagram of a generic human body showing a number of implanted medical devices.
[Para 68] FIGURE 2 is a fragmented perspective view of a prior art unipolar discoidal feedthrough capacitor.
[Para 69] FIGURE 3 is a sectional view of the feedthrough capacitor of FIG. 2 shown mounted to a hermetic seal of an active implantable medical device
(AIMD).
[Para 70] FIGURE 4 is a schematic diagram showing the feedthrough capacitor shown in FIGS. 2 and 3.
[Para 71 ] FIGURE 5 is a perspective view of a quadpolar feedthrough capacitor.
[Para 72] FIGURE 6 is sectional view taken along the line 6-6 of FIG. 5. [Para 73] FIGURE 7 is an electrical schematic diagram of the quadpolar feedthrough capacitor of FIGS. 5 and 6.
[Para 74] FIGURE 8 is an exploded electrode view showing the inner and outer diameter electrodes of the unipolar feedthrough capacitor of FIGS. 2 and
3.
[Para 75] FIGURE 9 is an exploded view of the interior electrodes of the quadpolar feedthrough capacitor show in FIG. 5.
[Para 76] FIGURE 10 is a perspective view of a quadpolar feedthrough capacitor mounted on top of a hermetic seal.
[Para 77] FIGURE 1 1 is a sectional view taken generally along the line 1 1 -1 1 of FIG. 10.
[Para 78] FIGURE 1 2 is an electrical schematic diagram of the quadpolar hermetic feedthrough terminal shown in FIG. 10.
[Para 79] FIGURE 1 3 is a perspective view of a monolithic ceramic capacitor
(MLCC).
[Para 80] FIGURE 14 is a sectional view taken generally along the line 14-1 4 of FIG. 1 3.
[Para 81 ] FIGURE 1 5 is an electrical schematic diagram of an ideal MLCC capacitor as illustrated in FIG. 1 3.
[Para 82] FIGURE 1 6 is a more realistic electric schematic diagram of the
MLCC structure of FIG. 1 3.
[Para 83] FIGURE 1 7 is a chart giving the formula for resonance frequency.
[Para 84] FIGURE 1 8 is a graph showing filter attenuation versus frequency. [Para 85] FIGURE 1 9 is a perspective view of a unipolar terminal having three different size MLCC capacitors connected to the feedthrough pin.
[Para 86] FIGURE 20 is an electrical schematic diagram of the structure shown in FIG. 1 9.
[Para 87] FIGURE 21 is a graph showing the attenuation response for the three chip capacitor unipolar hermetic terminal shown in FIG. 1 9.
[Para 88] FIGURE 22 illustrates a different method of mounting the MLCC capacitors such as those shown in FIG. 1 9.
[Para 89] FIGURE 23 illustrates a more desirable way to mount the capacitor of FIG. 22.
[Para 90] FIGURE 24 shows yet another way of mounting the MLCC capacitor of FIGS. 22 and 23.
[Para 91 ] FIGURE 25 is an electrical schematic diagram showing an equivalent circuit model for the MLCC chip capacitor.
[Para 92] FIGURE 26 is a perspective and schematic view of a prior art MLCC transient suppressant diode.
[Para 93] FIGURE 27 is an electrical schematic diagram of the diode of FIG.
26.
[Para 94] FIGURE 28 is a perspective and schematic diagram of a prior art chip inductor.
[Para 95] FIGURE 29 is an electrical schematic diagram of the inductor chip of
FIG. 28. [Para 96] FIGURE 30 is a perspective view of an MLCC capacitor having an inductor circuit trace deposited thereon.
[Para 97] FIGURE 31 is an exploded perspective view of a structure similar to FIG. 30 showing another way to deposit the inductor shape onto a separate substrate.
[Para 98] FIGURE 32 is a perspective view of a composite monolithic ceramic capacitor-parallel resonant tank (MLCC-T) or bandstop filter. [Para 99] FIGURE 33 is an exploded perspective view of the various layers of the MLCC-T tank filter of FIG. 32.
[Para 100] FIGURE 34 is an electrical schematic diagram of the MLCC-T tank or bandstop filter of FIGS. 32 and 33.
[Para 101 ] FIGURE 35 is a sectional view of one pole of a quadpolar feedthrough capacitor embodying an MLCC-T filter. [Para 102] FIGURE 36 is an electrical schematic diagram of the quadpolar device partially shown in FIG. 35.
[Para 103] FIGURE 37 is a perspective view of a prior art flat-through capacitor.
[Para 104] FIGURE 38 is a diagram showing the internal electrode array of the flat-through capacitor of FIG. 37.
[Para 105] FIGURE 39 is an electrical schematic diagram of the prior art flat- through capacitor of FIGS. 37 and 38.
[Para 106] FIGURE 40 illustrates the attenuation versus frequency response curve of the typical flat-through capacitor of FIGS. 37 and 38. [Para 107] FIGURE 41 is a perspective view of a quadpolar EMI filter hermetic seal similar to that shown in FIG. 10, but embodying a shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
[Para 108] FIGURE 42 is a sectional view taken generally along the line 42-42 of FIG. 41 .
[Para 109] FIGURE 43 is a sectional view taken generally along the line 43-43 of FIG. 41 .
[Para 1 10] FIGURE 44 is a sectional view taken generally along the line 44-44 of FIG. 41 .
[Para 1 1 1 ] FIGURE 45 is a sectional view taken generally along the line 45-45 of FIG. 41 .
[Para 1 12] FIGURE 46 is a sectional view taken generally along the line 46-46 of FIG. 41 .
[Para 1 1 3] FIGURE 47 is an exploded perspective view of the plates forming the flat-through EMI/energy dissipating filter of FIGS. 41 -46.
[Para 1 14] FIGURE 48 is a sectional view taken generally along the line 48-48 of FIG. 41 .
[Para 1 1 5] FIGURE 49 is an electrical schematic drawing of the flat-through
EMI/energy dissipating filter of FIG. 41 .
[Para 1 16] FIGURE 50 is a sectional view similar to FIGS. 43 and 44 illustrating incorporation of stacked layers Li and l_2 into a single co-planar layer.
[Para 1 1 7] FIGURE 51 is a sectional view similar to FIGS. 42-46, showing modification of the active electrode plates for connection to a via hole. [Para 1 18] FIGURE 52 is a fragmented perspective view illustrating a lead wire extending into one of the via holes of FIG. 51 .
[Para 1 19] FIGURE 53 is a view similar to FIG. 52, showing an alternative bond pad in place of the wire.
[Para 120] FIGURE 54 is a perspective view of a unipolar hermetic seal similar to that shown in FIG. 3, except that it is inverted with the feedthrough capacitor replaced with a shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
[Para 121 ] FIGURE 55 is a fragmented view of the area indicated by line 55-55 in FIG. 54, illustrating an alternative way of attaching a lead wire.
[Para 122] FIGURE 56 is a sectional view taken generally along the line 56-56 of FIG. 54.
[Para 123] FIGURE 57 is a fragmented sectional view showing an alternative connection methodology wherein a via hole is filled and then attached to a solder bump.
[Para 124] FIGURE 58 is an exploded perspective view of various components forming the structure of FIGS. 54 and 56.
[Para 125] FIGURE 59 is an electrical schematic for the structure of FIGS. 54,
56 and 58.
[Para 126] FIGURE 60 is a perspective view showing modification of an active electrode plate layer shown in FIG. 58.
[Para 127] FIGURE 61 is a view similar to FIG. 60, wherein the active electrode plate has been modified by adding a spiral inductor element. [Para 128] FIGURE 62 is an electrical schematic for the inductor-capacitor filter formed by the substrate of FIG. 61 .
[Para 129] FIGURE 63 is an exploded perspective view of a quadpolar filter assembly incorporating a shielded three-terminal flat-through EMI/energy dissipating filter in accordance with the present invention. [Para 1 30] FIGURE 64 is a top plan view showing a modification of the grounded shield plates of FIG. 63.
[Para 1 31 ] FIGURE 65 is a view similar to FIG. 64 of the grounded shield plates, showing additional modifications.
[Para 1 32] FIGURE 66 is similar to FIGS. 64 and 65, showing an alternative configuration of the grounded shield plates.
[Para 1 33] FIGURE 67 is a perspective view of an alternative arrangement of the active electrode plate substrate of FIG. 63.
[Para 1 34] FIGURE 68 is a graph illustrating attenuation versus frequency comparing the performance of the shielded three-terminal flat-through EMI/energy dissipating filter of FIGS. 63 with other technologies. [Para 1 35] FIGURE 69 is an exploded isometric view that is similar to FIG. 63 wherein the active electrodes have been modified to include inductors. [Para 1 36] FIGURE 70 is an exploded view very similar to FIGS. 63 and 69 except that edge shields and optional separating shields have been placed to prevent EMI radiation from the active electrode plates or optionally between co- planar electrode plates. FIGURE 71 is an exploded perspective view of an alternative form of the shielded three-terminal flat-through EMI/energy dissipating filter similar to
FIG. 63.
[Para 1 37] FIGURE 72 is an enlarged view of a round Wheeler spiral shown forming a portion of an active electrode plate in FIG. 69.
[Para 1 38] FIGURE 73 is similar to FIG. 72, showing a square Wheeler spiral such as those shown forming portions of the active electrode plates in FIGS. 69,
70 and 71 .
[Para 1 39] FIGURE 74 illustrates several typical inductor meander shapes.
[Para 140] FIGURE 75 illustrates the attenuation curves for various types of low-pass filters.
[Para 141 ] FIGURE 76 is a family of filter attenuation curves similar to that shown in FIG. 68.
[Para 142] FIGURE 77 is a perspective view of a bipolar hermetically sealed filter embodying the shielded three-terminal flat-through EMI/energy dissipating filter present invention.
[Para 143] FIGURE 78 is an exploded perspective view of the internal layers of the shielded three-terminal flat-through EMI/energy dissipating filter of FIG.
77.
[Para 144] FIGURE 79 is an exploded perspective view of an alternative embodiment embodying the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. [Para 145] FIGURE 80 is a partially fragmented view of the assembled section of FIG. 79 taken along the line 80-80 of FIG. 79.
[Para 146] FIGURE 81 is an electrical schematic diagram of the quadpolar shielded three-terminal flat-through EMI/energy dissipating filter shown in
FIGS. 79 and 80,
[Para 147] FIGURE 82 is an exploded perspective view of an inline hybrid substrate embodying the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention.
[Para 148] FIGURE 83 is an electrical schematic diagram of the structure shown in FIG. 82.
[Para 149] FIGURE 84 is an exploded perspective view of another form of a shielded three-terminal flat-through EMI/energy dissipating filter embodying the present invention.
[Para 1 50] FIGURE 85 is similar to FIG. 84 except that the diode array has been replaced with an RFID chip.
[Para 1 51 ] FIGURE 86 is similar to FIG. 84, wherein toroidal inductors have been used to replace a series of surface mount chip inductors.
[Para 1 52] FIGURE 87 is a view similar to FIG. 84, illustrating the flexibility of a portion of a hybrid substrate.
[Para 1 53] FIGURE 88 is an internal diagrammatic view of the novel hybrid substrate of FIG. 84.
[Para 1 54] FIGURE 89 is an electrical schematic diagram of the novel hybrid substrate of FIG. 84. [Para 1 55] FIGURE 90 is the same as one of the active circuits of FIG. 89 wherein the "T" circuit filter has been replaced with a π circuit filter.
[Para 1 56] FIGURE 91 is similar to FIG. 84, with the addition of a prior art quadpolar feedthrough capacitor.
[Para 1 57] FIGURE 92 is a plan view of the reverse side of the flexible portion of the hybrid substrate of FIGS. 84 and 88.
[Para 1 58] FIGURE 93 is a sectional view taken generally along the line 93-93 of FIG. 92.
[Para 1 59] FIGURES 94-97 are fragmented sectional views taken generally of the area indicated by the line 94, 95, 96 and 97 in FIG. 93, showing alternative methods of making an electrical connection.
[Para 160] FIGURE 98 is a plan view similar to FIG. 92 showing a modified version of flex cable assembly with four via holes.
[Para 161 ] FIGURE 99 is a cross-sectional view of the area indicated by line
99-99 in FIG. 93, showing type of yet another embodiment illustrating attachment of the substrate over a terminal pin utilizing a weld ring or a braze ring.
[Para 162] FIGURE 100 is a view similar to FIG. 99 illustrating yet another methodology of attachment.
[Para 163] FIGURE 101 is an isometric cross-section of a novel attachment cap used to connect the shielded three-terminal flat-through EMI/energy dissipating filter to various types of hermetic or non-hermetic seals. [Para 164] FIGURE 102 is a cross-sectional view of a prior art hermetic seal embodying the novel cap from FIG. 1 01 .
[Para 165] FIGURE 103 is a schematic view illustrating a methodology of having a circuit trace or a portion of an electrode plate dodge around a via hole.
[Para 166] FIGURE 104 is a schematic illustration of an alternative embodiment to FIG. 84.
[Para 167] FIGURE 105 is similar to FIG. 1 04, except that it illustrates the methodology of breaking up flex cable section of the hybrid substrate into flexible sections.
[Para 168] FIGURE 106 is an exploded perspective view of an in-line octapolar hermetic terminal with a shielded three-terminal flat-through EMI/energy dissipating filter hybrid flat-through substrate embodying the present invention.
[Para 169] FIGURE 107 is a flow chart illustrating a manufacturing production process.
[Para 1 70] FIGURE 108 is an exploded perspective view of a typical sixteen lead hermetic seal utilizing a novel hybrid shielded three-terminal flat-through
EMI/energy dissipating filter embodying the present invention.
[Para 1 71 ] FIGURE 109 is an electrical schematic diagram of the structure of
FIG. 108.
[Para 1 72] FIGURE 1 1 0 is a perspective view of a five pin terminal. [Para 1 73] FIGURE 1 1 1 is a perspective view of the five pin terminal of FIG.
1 10 to which a shielded three-terminal flat-through EMI/energy dissipating filter of the present invention is mounted.
[Para 1 74] FIGURE 1 1 2 is a perspective view similar to FIG. I l l , showing an alternative embodiment wherein reversed geometry MLCC's are utilized to provide high frequency attenuation.
[Para 1 75] FIGURE 1 1 3 is a flow chart illustrating an exemplary manufacturing process of the electronic components of the present invention.
[Para 1 76] FIGURE 1 1 4 is an illustration of an exemplary AIMD showing the use of variable impedance elements in connection with a lead wire within the housing of the AIMD.
[Para 1 77] FIGURE 1 1 5 is a schematic illustration of the structure shown in
FIG. 1 1 4, showing use of variable impedance elements on leads that ingress and egress the AIMD.
[Para 1 78] FIGURE 1 1 6 is a schematic illustration showing that a variable impedance element can be a capacitor element.
[Para 1 79] FIGURE 1 1 7 is a schematic illustration similar to FIG. 1 1 6, showing that the variable impedance element can be a feedthrough capacitor element.
[Para 180] FIGURE 1 1 8 is a schematic illustration similar to FIGS. 1 1 6 and 1 1 7, showing that the variable impedance element can be an L-C trap filter.
[Para 181 ] FIGURE 1 1 9 is a schematic illustration similar to FIG. 1 1 8, showing use of a capacitor element in parallel with the L-C trap filter. [Para 182] FIGURE 1 20 is similar to FIG. 1 1 5 with emphasis on the series variable impedance element.
[Para 183] FIGURE 1 21 illustrates that the variable impedance element can be an inductor.
[Para 184] FIGURE 1 22 illustrates that the variable impedance element can be an L-C bandstop filter.
[Para 185] FIGURE 1 23 is an attenuation versus frequency chart showing impedance characteristics of various types of filters.
[Para 186] FIGURE 1 24 is a schematic diagram of a series inductor-capacitor filter commonly known in the industry as an L-C trap filter.
[Para 187] FIGURE 1 25 is a chart giving the resonant frequency equation for an L-C series trap filter.
[Para 188] FIGURE 1 26 illustrates the impedance Z in ohms versus frequency of the series resonant L-C trap filter of FIG. 1 24.
[Para 189] FIGURE 1 27 is similar to the chart similar to FIG. 1 26, illustrating the impedance in ohms versus frequency of two discrete series resonant L-C trap filters.
[Para 190] FIGURE 1 28 is an overall outline drawing showing a cardiac pacemaker with endocardial lead wires implanted into a human heart.
[Para 191 ] FIGURE 1 29 is a cross-sectional view of a human head showing a deep brain stimulator electrode.
[Para 192] FIGURE 1 30 is a schematic illustration of a unipolar lead system for an AIMD. [Para 193] FIGURE 1 31 is an illustration similar to FIG. 1 30, including an L-C trap filter.
[Para 194] FIGURE 1 32 is another illustration similar to FIG. 1 30, wherein the frequency selective components comprise capacitive elements. [Para 195] FIGURE 1 33 is another illustration similar to FIGS. 1 30 and 1 32, wherein the capacitance value C has been selected such that the capacitive reactance will be equal and opposite to the inductive reactance of the implanted lead.
[Para 196] FIGURE 1 34 illustrates prior art hermetic and non-hermetic connectors that are typically used in the military, aerospace, medical, telecommunication and other industries.
[Para 197] FIGURES 1 35 and 1 36 illustrate a prior art sub D-type connector. [Para 198] FIGURE 1 37 and 1 38 show prior art hermetic connectors. [Para 199] FIGURE 1 39 shows an exploded view of a prior art multi-pin connector and a shielded three-terminal flat-through EMI filter. [Para 200] FIGURE 140 is similar to FIG. 1 39 except that the shielded three- terminal flat-through EMI filter of the present invention has been attached. [Para 201 ] FIGURE 141 is an exploded view taken generally from section 1 41 - 1 41 of FIG. 1 39 showing a surface mounted MLCC capacitor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[Para 202] As shown in the drawings for purposes of illustration, the present invention is concerned with shielded three-terminal flat-through EMI/energy dissipating filters 1 90 which can be embodied in substrates or flex cable assemblies. The novel concept resides in designing an embedded flat-through capacitor wherein optional surface mounted passive or active components can be attached while at the same time providing an interconnection circuit. The novel shielded three-terminal flat-through EMI/energy dissipating filters 1 90 embody a flat-through capacitor that has similar characteristics to prior art feedthrough EMI filter capacitors. The flat-through EMI/energy dissipating filter 1 90 of the present invention provides three-terminal capacitive filtering while simultaneously providing shielding of circuits and signals passing through the robust high current capability electrodes of the flat-through capacitor. The flat-through EMI/energy dissipating filter 1 90 of the present invention functions in a very equivalent manner to prior art feedthrough capacitors in that: a) its internal ground plates act as a continuous part of the overall electromagnetic shield housing of the electronic device or module which physically blocks direct entry of high frequency RF energy through the hermetic seal or equivalent opening for lead wire ingress and egress in the otherwise completely shielded housing (such RF energy, if it does penetrate inside the shielded housing can couple to and interfere with sensitive electronic circuitry); and, b) like prior art feedthrough capacitors, the flat-through EMI/energy dissipating filter 1 90 of the present invention very effectively shunts undesired high frequency EMI signals off of the lead wire (electrodes) to the overall shield housing where such energy is dissipated in eddy currents resulting in a very small temperature rise. Of course, unlike for prior art discoidal/feedthrough capacitors, in the present invention the circuit currents (for example pacemaker pacing pulses or ICD HV defibrillation high current shocks) must pass through the internal electrodes of the embedded flat-through capacitor. By integrating flat-through technology into prior art circuit boards, substrates or flex cables, the flat-through electrodes can be manufactured with much thicker electrodes (like copper sheet) which greatly increases their capability to safely carry relatively higher through circuit currents (like external or internal cardiac defibrillation pulses).
[Para 203] FIGURE 41 is a very similar to the quadpolar EMI filtered hermetic seal that was illustrated in FIG. 10. In FIG. 41 , in accordance with the present invention, the feedthrough capacitor element has been completely eliminated, thus significantly reducing the cost of manufacture. The feedthrough capacitor 1 32 and its associated wire bond substrate 1 36 that were described in FIG. 1 0 have been replaced by a novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90. In FIG. 41 , wire bond pads 1 38, 1 38', 1 38", 1 38'" and 1 40 are very similar to the wire bond pads illustrated in FIG. 1 0. They are attached to a relatively higher K ceramic or suitable hybrid substrate 1 92. Novel parasitic flat-through capacitors of the present invention are integrated into the substrate 1 92. This is better understood by referring FIGURES 42 through 46.
[Para 204] FIG. 42 illustrates a grounded shield plate 1 94. In this case, the center pin 1 96 is grounded. That is, there is a web plate (not shown) underneath the substrate 1 92 wherein the ground pin 1 96 is electrically coupled to the metallic ferrule 1 20 of the hermetic seal 1 1 2. It is important that this be a low inductance RF ground. In other words, the web plate would be a high surface area plate with clearance holes only for the pass through of lead wires 1 1 4, 1 14', 1 14" and 1 14'". This RF grounded web plate, could, for example, have its outer diameter laser welded to the ferrule 1 20 of the hermetic terminal and its inside diameter hole welded or soldered to the grounded lead wire or pin 1 96. An alternative methodology of grounding the center pin 1 96 is illustrated with embedded ground plates within the hermetic seal as shown in FIG. 48. Referring to FIG. 48, one can see that there is a hermetic insulator 1 1 8 through which the lead wires pass in non-conductive relation to the metallic ferrule 1 20. Shown are ground plates 1 98 embedded in the insulative portion 1 1 8 of the hermetic seal 1 1 2 which are attached by gold brazing to the center ground pin 1 96. Grounding this centered pin 1 96 using plates embedded in the insulator 1 1 8 of the hermetic seal 1 1 2 has been described in U.S. Patent No. 7,1 99,995, the contents of which is incorporated herein by reference. Other methods of grounding pin 1 96 are further described in U.S. Patent Nos. 5,905,627 and 6,529, 103, the contents of which are also incorporated herein by reference.
[Para 205] FIGS. 43 through 46 illustrate the internal active electrode plate layouts 1 76, 1 76', 1 76" and 1 76'". The overlap area which is otherwise known as the effective capacitance area (ECA) of each of these active electrode plates has been maximized in order to maximize the flat-through capacitance. Maximizing the thickness and the area of the active electrode plates 1 76-1 76'" also has an added benefit in that their overall resistance is lowered (and its current rating is greatly increased). This is important because circuit currents of the novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 must pass through the respective electrode plates 1 76-1 76'" in order to accomplish the novel shielded flat-through capacitor characteristics. [Para 206] As previously mentioned, one serious negative to prior art flat- through capacitors 1 74, such as shown in Fig. 37, is that it is not conveniently mountable in such a way that it becomes an integral part of an overall electromagnetic shield. There is always a frequency at which undesirable RF coupling 1 88 across the device will occur. This usually does not happen until 1 00 MHz or above. At very high frequencies, such as above 1 GHz, this problem becomes quite serious. A second negative, as compared to prior art discoidal feedthrough capacitors 1 1 0 and 1 32, where the circuit current runs through a robust lead in a feedthrough hole), is that the flat-through circuit currents must flow through the electrodes of the flat-through capacitor 1 74 itself. Limitations on electrode thickness and conductivity means that prior art flat-through capacitors 1 74 have relatively high series resistance and can only be rated to a few milliamps amps, or at best, a few amps. However, a patient's pacemaker lead undergoing external (AED) defibrillation or an implantable defibrillator must deliver a high voltage pulse of over 20-amps. The novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention overcomes both of the foregoing negatives associated with prior art flat-through capacitors by incorporating grounded shield plates 1 94 surrounding on at least the top and bottom sides a novel high surface area and relatively thick flat-through active electrode plate 1 76 through which circuits of up to 30-amps or greater can pass. As will be see in subsequent drawings, the novel high surface area electrodes 1 76 of the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 can optionally include inductor sections which not only desirably add series inductance to the filter but also increase the flat-through capacitance by increasing the effective capacitance area (ECA).
[Para 207] The overall internal construction of the novel hybrid substrate 1 92 is best understood by referring to the exploded view shown in FIGURE 47. One can see that each one of the flat-through active electrodes 1 76 through 1 76'" are sandwiched between a plurality of grounded shield plates 1 94, 1 94', 1 94", 1 94'", 1 94'" and 1 94"" as shown. The resulting high ECA has the effect of creating a very high value of flat-through capacitance for EMI filtering (typically several tens or hundreds of picofarads). In contrast, the narrow (low surface area) circuit trace-type flat-through designs taught by U.S. Patent Nos. 5,683,435 and 6,473,314 are not effective capacitor electrodes. This results in a flat-through capacitance that is nearly zero (only a stray picofarads which offers no effective EMI filter attenuation by itself). In addition, by creating the flat-through capacitance between overlapping grounded shield plates 1 94, the problem that was previously described in connection with the prior art structure of FIG. 37 has been eliminated. In FIG. 37, it was shown that for a typical prior art flat-through capacitor, there is a frequency at which coupling 1 88 will occur. This is where the RF signal can, through stray capacitance, antenna action or mutual inductance, avoid passing through electrode plate 1 75 and instead be coupled directly across the circuit traces or couple to adjacent circuit traces. This is best understood as previously described in FIG. 40 as the degradation and attenuation due to cross-coupling. By shielding the high surface area electrodes 1 76 of the novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention with RF grounded shield plates 1 94 on both sides (and optionally co-planar sides as well), this stray coupling problem and associated high frequency attenuation degradation has been completely eliminated. Again, referring to FIG. 37, one can see that there is really no shield barrier from end-to-end of a prior art flat-through capacitor 1 74. At some frequency, for example around 1 00 MHz to 1 GHz, EMI or RF will undesirably cross-couple across the prior art flat-through capacitor 1 74 or, potentially worse yet, couple to adjacent circuits. [Para 208] Referring back to the novel construction as illustrated in FIGS. 41 through 48, the flat-through capacitance is very well shielded. In this case, the flat-through capacitance will act as an ideal capacitor and will be free of resonances and parasitic RF coupling degradation. In FIG. 48, one can see an optional external metallization 1 08 that is connected to the interior grounded shield electrode plates 1 94. This is useful to help prevent edge re-radiation of high frequency RF energy which could couple to sensitive electronic circuits inside the overall shielded housing of the electronic device. In a preferred embodiment, the external metallization 1 08 would be directly electrically connected to gold braze 1 24 (in this case, the diameter of the ferrule 1 20 would need to be enlarged. Accordingly, the RF grounding and impedance would be lowered between the ferrule 1 20 and the outer metallization 1 08 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90. In this case, it will be obvious that the center ground pin 1 96 could be eliminated and the internal ground electrodes 1 98 within the hermetic insulator 1 1 8 could also be eliminated. In other words, the grounding of the shield electrode plates 1 94 could be accomplished either by the center pin 1 96 as shown in FIG. 48, or be done around the outside perimeter or circumference with an attachment between the external metallization 1 08 and for example, gold braze 1 24. Adding metallization 1 08 means that the embedded active flat-through electrode plates 1 76 are RF shielded by top and bottom plates 1 94 and on their co-planar edges by shield 108. This means that the active electrode plates 1 76 are completely shielded such that RF re-radiation or cross coupling cannot occur.
[Para 209] Referring once again to FIG. 48, there is an insulative washer 200 which is disposed between the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 and the hermetic insulator body 1 1 8. This is to make sure that the electrical connection materials 1 28 cannot migrate underneath the hybrid substrate 1 92 and cause shorting between adjacent pins. For example, if electrical conductive material 1 28 were to migrate between pins 1 1 4" and 1 14'" this could short out the output of a cardiac pacemaker. Insulating layer 200, in a preferred embodiment is also an adhesive. This is desirable during manufacturing such that the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 is firmly affixed to the hermetic seal 1 1 2. This makes the subsequent electrical attachment operations by soldering, centrifuging of thermally conductive polyamides or epoxies or the like, more convenient. [Para 210] Referring once again to FIG. 48, the body fluid side is shown on the bottom side of hermetic insulator 1 1 8. It is typical that electronic circuits for AIMDs be inside the hermetic and electromagnetically shielded housing. However, the present invention is not limited to only placing the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 on the inside of the housing of the AIMD. If one were to construct the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of entirely biocompatible materials, there is no reason that it could not be disposed on the body fluid side. Reference is made to U.S. Patent 7,1 1 3,387 the contents of which are hereby incorporated herein, which describes EMI filter capacitors designed for direct body fluid exposure. For example, active flat-through electrodes and their corresponding electrode shield plates could all be disposed within a non- lead containing high dielectric material and with connections and electrodes and shield plates made of biocompatible materials such as pure platinum, gold, niobium, tantalum, titanium or the like. In other words, the structure of FIG. 48 could be constructed such that it would be adapted for direct body fluid exposure.
[Para 21 1 ] FIGURE 49 is a schematic drawing of the novel shielded three- terminal flat-through EMI/energy dissipating filter 1 90 of FIG. 41 . Shields 1 94 through 1 94"" illustrate the fact that the high surface area active electrode plates 1 76 are surrounded at least on top and bottom by grounded shield electrode plates 1 94 that form the flat-through effective capacitance overlap area and at the same time prevent undesirable RF coupling across the flat- through capacitive filter. The feedthrough capacitances Ci , C2, C3 and C4 have been formed by the overlap area (ECA) between each of the active electrodes 1 76 and the corresponding shield plates 1 94 that surround the active electrodes on both top and bottom. For example, referring back to FIG. 47, one can see that active electrode plate 1 76-1 76'" have been surrounded on top and bottom by grounded shield plates 1 94-1 94"". The grounded shield plates 1 94" can be deposited by metal plating, thick film deposition (silk-screening), discrete metal sheets or similar processes on to a dielectric layer which has a specific dielectric thickness d. It is well known to capacitor designers that the formula for the total flat-through capacitance is given by the formula C=kA(n- ])/d. In this formula, k is the permittivity or dielectric constant of the insulative dielectric material itself; A is the effective capacitance area in in2 or mm2 (ECA) determined by the overlap of the grounded shield plates 1 94 and 1 94' and, for example, the active electrode 1 76; n is the number of total electrode areas; and, d is the dielectric thickness. Referring to FIG. 47, we can add can add insulative dielectric cover sheets (not shown) which can be the same or different insulating and/or dielectric material that forms the dielectric layer on each of the electrode layers (this is to add additional electrical and mechanical protection). It will be obvious to those skilled in the art of designing capacitors that blank cover sheets (as many as needed) could also be inserted between the active electrode layers 1 76 and the associated or surrounding grounded shield plate layers 1 94. This would cause the dielectric thickness d to become greater which would have two effects. The first effect would be to increase the dielectric thickness and therefore the voltage rating of the flat-through capacitor. Thin dielectric layers tend to break down at relatively lower voltages. Therefore, for a high voltage application, such as that of an implantable cardioverter defibrillator (ICD), one would want a dielectric thickness that would be relatively greater than say, for example, a low voltage pacemaker. When one examines the equation for capacitance, the dielectric thickness d appears in the denominator. So as one increases the dielectric thickness then the total flat- through capacitance would drop. Accordingly, the first decision a designer makes is what is the required dielectric thickness for the voltage rating of the application and then adjust the ECA such that the desired flat-through capacitance is achieved. In some cases, not enough flat-through capacitance will be achieved to adequately filter all frequencies. As will be described in connection with subsequent drawings, it will be shown how to add, by surface mounting or embedding or thick film deposition, commercially available discrete capacitors, inductors, diodes and other components to enhance its overall performance of the present invention, and in particular, the low frequency performance of the novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90. [Para 212] FIGURE 50 illustrates a way to produce the novel hybrid EMI filter substrate 1 92 of FIG. 41 with less layers and a correspondingly lower overall substrate thickness. This is accomplished by incorporating two (or more) active electrode 1 76 and 1 76' onto a single co-planar layer. Putting multiple active electrode plates on co-planar layers has the desired effect of making the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 thinner, easier to manufacture and less expensive. However, this has the undesirable effect of reducing the effective capacitance area (ECA) for each active electrode plate 1 76. However, when high K materials are used, the effective capacitance area is so large that this is really not a detriment. Also, subsequent drawings will show methods of adding co-planar inductor-electrodes to boost the filter attenuation. It will be obvious to those skilled in the art that in a similar manner, active electrodes 1 76" and 1 76'" could also be incorporated into a single combined layer. The novel shielded three-terminal flat-through EMI/energy dissipating filter 1 90, and particularly its hybrid substrate 1 92, can be constructed of prior art flex circuit techniques (like polyimide flex circuits), multilayer rigid substrates (like alumina or FR4 board), thick film deposition onto a substrate or carrier, or the like. For each of these manufacturing techniques, there is a practical limit to the number of layers that can be built up. This limitation has to do with limitations of the inherent manufacturing process. For example, when one builds up a sufficient number of layers (more than 8 to 10), then a flex circuit starts to become fairly rigid. In fact, it's common in flex cable design that a portion of the flex cable be built up and become a portion known as "rigid-flex." The present invention allows the shielded three-terminal flat-through EMI/energy dissipating filter technology to be used in completely flexible substrates, hybrid substrate designs that have both a flexible and a rigid layer, or in a completely rigid board. [Para 21 3] Referring back to FIG. 41 , one can see that there are wire bond pads 1 38 through 1 40 as shown. The addition of wire bond pads adds a circuit connection convenience and an additional expense. In comparison, FIG. 51 , shows that, for example, the active electrode plate 1 76 shown in FIG. 43 could be modified such that it was connected to a via hole 202. This via hole 202 provides for a convenient connection of either a lead wire 204, as shown in FIG. 52, or a round (or rectangular, square or other not shown) wire bond pad 206 as illustrated in FIG. 53.
[Para 214] FIGURE 54 is an isometric drawing of a unipolar pacemaker hermetic seal 1 1 2 that is similar to that shown in FIG. 3 except that the feedthrough capacitor has been replaced with a shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention shown mounted on top of the insulator 1 1 8 and gold braze 1 24. The hybrid substrate 1 92 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 can be manufactured from any number of the techniques previously described herein.. The body of the hybrid substrate 1 92 could be a conventional substrate consisting of high dielectric constant ceramic, alumina, ceramic, fiberglass, FR4 or any other rigid type of multi-layer board technology. In addition, it could be made of a number of flexible or flex cable variances. These could include flex cables that are laminated together based on polyimide, Kapton and acrylic construction. Another embodiment would be polyimide flex cables with all polyimide connections which are laminated together at high temperature. All of these types of boards and/or substrates and/or flex cables are known in the art. What is described herein is a very novel adaptation of those boards and substrates to flat-through filter technology. Hereinafter, the novel substrates incorporating various forms of novel shielded flat-through EMI filter technologies will be referred to as the hybrid substrates 1 92. [Para 21 5] In FIG. 54, one can see that there is a metalized area 208 on the hybrid substrate 1 92. This wrap-around metalized area 208 makes connection to internal ground shield plates 1 94 and 1 94' embedded within the hybrid substrate 1 92 as shown in Fig 56. One can see in FIG. 54 a plurality of electrical connections 210,21 0' and 21 0 '" as shown (the equivalent electrical connections 210" and 21 0"" on the opposite side of substrate 1 92 are not shown). These electrical connections connect to gold braze 1 24 that is part of the hermetic seal and provides an "oxide-free" RF ground multi-point connection. This is better understood by referring to FIG. 56 which is taken from section 56-56 of FIG. 54. The importance of connecting to a gold braze instead of connecting directly to the titanium ferrule 1 20 can be better understood by referring to U.S. Patent Nos. 6,765,779 and 6,765,780 the contents of which are incorporated herein. From FIG. 56, one can see that there is a prior art hermetic seal 1 1 2 which includes a metal ferrule 1 20 which is typically of titanium or the like. There is a flange area 21 2 shown which is convenient for laser welding to the titanium housing of an AIMD, such as a cardiac pacemaker or the like. There is a hermetic insulator 1 1 8 which can be of alumina, ceramic materials, glass or equivalent. In this particular embodiment, there is a gold braze 1 24 which forms a mechanical and hermetic seal between the insulator 1 1 8 and the ferrule 1 20. A gold braze 1 22 makes a similar mechanical and hermetic seal between the lead wire 1 1 4 and the insulator 1 1 8. In this example, the body fluid side would be towards the bottom of the cross-sectional illustration of FIG. 56. An electrical connection is made between lead wire 1 1 4 and the metalized via hole 202 which is part of the novel hybrid substrate 1 92. The via hole 202 makes electrical connection to internal active electrode (otherwise known as the flat-through electrode) plate 1 76 as shown, which in turn is connected to via hole 202'. The grounded electrode shield plates 1 94 and 1 94' are connected to the outside metallization surface 208 of the hybrid substrate 1 92. In turn, this metallization 208 is electrically connected via material 210 to the gold braze 1 24 of the hermetic seal 1 1 2. As previously stated, this direct connection to gold makes a reliable oxide free low impedance connection, the importance of which is described thoroughly in U.S. Patent Nos. 6,765,779 and 6,765,780. One can also see that by wrapping metallization surface 208 around the sides of the hybrid substrate 1 92, one prevents any chance that EMI being conducted on active electrode 1 76 could radiate or cross-couple into the interior of the AIMD. By keeping the EMI "bottled up" between the grounded shield plates 1 94 and 1 94', one forms a nearly complete faraday cage shield which is the ideal solution. Due to the thin geometry, substrate edge re-radiation of RF energy is a very minor concern which, if the dielectric thickness between layers 1 76 and 1 94, 1 94' becomes large, can be solved by co-planar edge shields which will be described in connection with FIG. 60. This novel method of shield containment is applicable to any of the embodiments described herein.
[Para 216] Referring once again to FIG. 54, one can see that a prior art monolithic ceramic chip capacitor (MLCC) 1 42 has been electrically connected to lands which are in turn connected to via holes 202' and 202". This is better understood by referring to the exploded view of Fig. 54 shown in FIG. 58. One can see that via hole 202' is connected to the active circuit electrode 1 76. The other side of the MLCC capacitor 1 42 is connected by via hole 202" to both of the grounded shield electrode plates 1 94 and 1 94'. It is important that a very low impedance connection has been made to both sides of the MLCC capacitor 1 42. In this embodiment, any type of chip capacitor could be used. That is, monolithic ceramic, stacked film, tantalum, electrolytic or the like. It will also be obvious to those skilled in the art that the ground (left) side of MLCC capacitor 1 42 need not be connected to RF ground by way of the via 202" as shown. Instead, an enlarged land on the left side of the MLCC 1 42 could be RF grounded directly to the external wrap-around metallization surfaces 208.
[Para 21 7] In FIG. 54, one can see that there is a wire bond pad 1 38 which is affixed to the hybrid substrate 1 92. This makes for a convenient mounting pad for attachment of lead wire 204. Lead wire 204 would be routed to the internal circuits of the general electronic device or an AIMD. Lead wire 204 can be affixed to wire bond pad 1 38 by thermal or ultrasonic welding, soldering or the like. FIG. 55 shows an alternative arrangement wherein the wire bond pad 1 38 (which would typically be made of Kovar) has been eliminated. In FIG. 55, there is a different type of plated of metal deposited wire bond pad 1 39. In this case, no separate attachment of a Kovar block 1 38 is required as illustrated in FIG. 54. In this case, in FIG. 55, wire bond pad 1 39 can be an integral part of an external circuit trace and deposited by plating, thick film deposition technique and the like.
[Para 218] Referring once again to FIG. 56, active electrode plate 1 76 is sandwiched between the two grounded electrode shield plates 1 94 and 1 94'. The prior art MLCC capacitor 1 42 is connected between via hole 202' (which is also connected to the active circuit plate 1 76) and via hole 202" which is in electrically conductive relationship with both the ground shields 1 94 and 1 94'. Electrically speaking, this means that the MLCC capacitor 142 connects from the active circuit plate 1 76 to ground. Accordingly, it acts as an electrical bypass low-pass filter element to provide additional EMI filtering to complement the flat-through capacitance as previously described. [Para 219] Referring once again to FIG. 56, one can see that there is an electrical connection material 214 that is disposed between the lead wire 1 14 and the via hole 202. This can be of a thermal setting conductive polymer, such as a conductive epoxy or a conductive polyimide or the like. Material 21 4 could also be of solder or braze, which is known in the art as solder bump construction or even ball grid array (BGA). It is shown in the reflowed position so it is not obvious that this started out as a round ball. In order to provide electrical isolation between this material 214 and the gold braze 1 24, one or more adhesive backed insulative washers 200 are disposed between the hermetic seal 1 1 2 and the hybrid substrate 1 92. Typically this washer 200 would be an adhesive backed polyimide or the like to make sure that electrical conductive materials such as 21 4 stay in place and could not short and/or migrate to areas where they were not desired (like a short to ground). As described in U.S. Patent No. 7,327,553, the contents of which are incorporated herein by reference, a laminar leak detection path can be provided between the washer 200 to facilitate helium leak testing of the hermetic seal. [Para 220] There is a similar electrical connection material 21 0 disposed between metallization surface 208 and gold braze 1 24. Material 21 0 is also typically a thermal setting conductive adhesive, solder, low temperature braze, laser weld, or the like. A wire bond pad 1 38 is shown connected to the active electrode plate 1 76. At this point, any electrical noise (EMI) that was entering from the body fluid side on lead wire 1 14 has been decoupled by the filtering action of the flat-through capacitances shown in FIG. 56 as Cp and Cp' and the MLCC 142 working together. The flat-through capacitance is relatively lower in value than the MLCC 1 42; however, it is very effective for attenuating high frequencies. Lower frequencies are attenuated by the higher capacitance value MLCC capacitor 142. Wire bond pad 1 38 is convenient for connection of one or more lead wires 204 to internal circuit components inside of the general electronic shielded module or an AIMD.
[Para 221 ] In FIG. 56 one can see that via hole 202 is connected to lead wire 1 14 by means of an electrical conducting material 21 4 which can be solder, a low temperature braze, a thermal-setting conductive adhesive or the like. An alternative methodology is shown in FIG. 57 wherein the via hole 202 is filled and then attached to a solder bump 21 6 as shown. The solder bump 21 6 makes contact to the metallization 1 06 of via hole 202. By raising the entire assembly to an elevated temperature, the solder bump 21 6 wets to the nail head lead 21 8 forming a reliable electrical and mechanical connection. [Para 222] FIGURE 58 is an exploded view of FIG. 54. A low impedance RF electrical connection to the ground shield plates 1 94 and 1 94' is very important. Accordingly, one can see that there are multiple electrical attachments 21 0 to 210"". This, of course, could be one long continuous connection all around the ground metallization 208 to the gold braze 1 24. However, it is desirable to not block a helium leak path. The integrity of these hermetic terminals is critical to preclude the entry of body fluid into the AIMD. [Para 223] Referring once again to FIG. 56, one can see that if there were a crack 220 or other defect in the hermetic terminal insulator 1 1 8 or in the corresponding gold braze 1 22 then body fluid (moisture) may be able to enter into the enclosed electronic housing or worse yet, the hermetic housing of an AIMD like a cardiac pacemaker. It is very common in the art to test these terminals using helium as a leak detection medium. However, a concern is that the installation of adjunct components, such as the hybrid substrate 1 92 of the present invention, could temporarily block the flow of helium. Typically a helium leak test is performed in a few seconds. Therefore any adjunct sealant, such as a continuous coverage of conductive thermal setting adhesive 210 or the like, could slow down the flow of helium through such coverings. Accordingly, in the preferred embodiment of the present invention, it is desirable to leave open gaps as shown in FIGS. 54 and 58 between areas of electrical attachment. In this way, if there are any defects 220 in the hermetic terminal insulator 1 1 8 or its associated gold brazes 1 22 and 1 24, the helium will be free to pass and be detected by the leak test equipment. As taught by U.S. Patent No. 6,566,978, the contents of which are incorporated herein by reference, it will be obvious to those skilled in the art that strategically placed open via holes through the hybrid substrate 1 92 could be provided in order to pass helium during hermetic seal testing.
[Para 224] Referring once again to FIG. 58, a novel aspect of the present invention is that flat-through capacitance develops between the circuit active electrode plate 1 76 and the surrounding grounded shield electrode plates 1 94 and 1 94'. This capacitance is shown as Cp and Cp'. The capacitance value of this flat-through capacitance is dependent upon the typical capacitance equation, which is given by C = kA(r\ -l )/d. Where k is the dielectric constant of the material. As previously mentioned, the novel hybrid substrate 1 92 shown in FIG. 56 could be constructed of a variety of different materials. For example, the dielectric constant of a polyimide material would be between 3 and 4 whereas an alumina ceramic material could be as high as 9 to 1 1 . Barium and strontium titinate dielectric bodies can have dielectric constants in excess of 5000. In the equation, A stands for the area, which is the effective capacitance area (ECA). This is calculated by the sandwiched overlap between the area of circuit active electrode plate 1 76 and the corresponding ground electrode shield plates 1 94 and 1 94'. Ignoring fringe effects, a simplified way of calculating this area is simply the area of active electrode plate 1 76 that is bounded between the sandwiched grounded shields 1 94 and 1 94'. In the equation, r\ is the total number of repetitive electrode plates. In this case, there are three plates consisting of 1 94, 1 76 and 1 94'. This gives us r\-l which yields two parasitic flat-through capacitances Cp and Cp'. The dielectric thickness d is simply the thickness of the dielectric material that separates 1 94 and 1 76; and 1 76 and 1 94' as shown. The presence of the flat-through capacitances Cp and Cp' is extremely important to the overall broadband EMI filtering performance of the present invention. This can be understood by referring to the schematic diagram of FIGURE 59. In addition to the flat- through capacitances Cp, Cp' ... Cpn,, there is also parasitic inductance formed along the length of the active electrode plate 1 76. This is shown as Lp, Lp- and Lpn. It will be obvious to those skilled in the art that the higher the amount of the effective capacitance area that overlaps between the active electrode place 1 76 and the adjoining ground shield plates 1 94 and 1 94', the higher the parasitic capacitance Cp will be. In this case, the parasitic inductance is very small and really does not aide in filtering. It will also be obvious to those skilled in the art that the parasitic inductance of the active electrode 1 76 will be proportional to both its length and its width. In other words, the longer the active electrode 1 76 is, the greater its inductance Lp will be. The presence of series inductance is very important as this will improve the overall high frequency performance of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90. There are ways of making this slight series parasitic inductance much higher as will be described below.
[Para 225] Referring back to schematic FIG. 59, one can see that in a number of locations there is a shield symbol 1 94-1 94'" (sometimes shown as "Sh"). This is an indication that the entire assembly consisting of the flat-through capacitance Cp and the capacitance C contributed by the MLCC capacitor 142, in general, has its active electrode all contained (sandwiched between) within the shield plates 1 94. As previously mentioned, this is very important so that undesirable electromagnetic interference at high frequency cannot bypass or jump across from the body fluid side and thereby enter into the electronic device or AIMD housing and possibly interfere with sensitive electronic circuits. The importance of filtering for AIMDs, such as cardiac pacemakers, has been described by U.S. Patent Nos. 4,424,551 , 5,333,095 and 5,905,627 the contents of which are incorporated herein. In this regard, the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 of the present invention acts in equivalent way to prior art feedthrough capacitors in that the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 is not only an effective filter and energy dissipation element, it's ground electrode plates 1 94 act as an effective part of the overall electromagnetic shield housing of the AIMD or other equivalent shielded electronic circuit. [Para 226] Referring back to FIG. 58, one can see that in the present configuration, the inductance, although quite small, is relatively maximized due to the relatively long length of active electrode plate 1 76 and the fact that it is relatively narrow. One will also notice that the flat-through (parasitic) capacitance is the sum of the parallel combination of Cp and Cp- and is relatively maximized due to the large area of the active electrode 1 76 and the high ECA achieved by its overlap with the grounded shield plates 1 94 and 1 94'. One way to further increase the total amount of flat-through (parasitic) capacitance would be to increase the number of layers in FIG. 58. In a monolithic construction, repeating the number of redundant layers would increase the capacitance by the r\-l term of the capacitance equation. Additional ways to increase the amount of flat-through capacitance would be to further increase the effective capacitance overlap area ECA, increase the dielectric constant or decrease the dielectric thickness (d).
[Para 227] Prior art feedthrough capacitors, as illustrated in FIGS. 2 and 5 and shown in the assembly in FIG. 1 0, make for very low inductance broadband low-pass filters. This is why they have generally been the preferred EMI filter at the point of lead wire ingress and egress for AIMDs and other devices. However, feedthrough capacitors are generally built in low volumes in the industry. Because of this, they tend to be relatively high in price when compared to the much higher volumes MLCC capacitors. It is not unusual for a single feedthrough capacitor to cost several dollars, wherein an MLCC capacitor can cost just a few cents. In addition, prior art feedthrough capacitors tend to be quite low in capacitance value (primarily in the range from 400 to 4000 picofarads). This means that prior art feedthrough capacitors make very effective high frequency filters above 25 MHz, but off little attenuation at low frequencies (below 5 MHz). Feedthrough capacitors, in general, can be a hundreds of times more costly than equivalent value MLCC capacitors. However, referring back to FIG. 1 3, for the MLCC capacitor and its high frequency performance curve, as illustrated in FIG. 1 8, this does not produce a broadband low-pass filter. In general, MLCCs are marginal or insufficient for attenuating high frequency emitters that AIMD patients can be exposed to. This includes cellular telephones, RF identification (RFID), airport radars, microwave ovens and the like. As described in connection with FIG. 37, one possible solution would be to use flat-through capacitor technology. However, the parasitic degradation of attenuation due to cross-coupling as illustrated in FIG. 40 is a serious problem. Another problem associated with the prior art flat-through capacitor of FIG. 37 is that it is relatively costly. This is not just because it is produced in relatively low volumes. There are additional costs required for the additional flat-through terminations 222 and 222' as shown in FIG. 37. These added terminations are difficult to automate and add significant hand work and additional expense. By incorporating the flat-through capacitor electrode plate 1 76 as a distributive parasitic element sandwiched between ground shield plates 1 94 and 1 94', as illustrated in FIG. 58, a number of desirable goals are achieved. First of all, the problem of cross-coupling across the flat-through capacitor has been eliminated. This is because it is contained or sandwiched within an entirely shielded structure. Therefore, there is no way for high frequency EMI to couple across the novel shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention. In addition, flex cables for circuit boards are already commonly used in prior art electronic devices including AIMDs. In other words, by not adding any additional structures, one can embed a flat-through capacitance and then combine it with an MLCC capacitor 1 42 (or additional components) as shown in FIG. 58. The MLCC capacitor 142 is effective for low frequency attenuation and the parasitic flat-through capacitance Cp works to attenuate high frequencies. The parasitic capacitance or flat-through capacitance works in parallel with the capacitance of the discrete MLCC capacitor 142 which results in a very effective broadband low-pass filter from kilohertz frequencies all the way to 1 0 gigahertz or higher. This is all summarized by the schematic diagram shown in FIGURE 59. Shields 1 94-1 94n are illustrative to indicate that the entire flat-through filter is sandwiched between RF shield plates in such a way that high frequency EMI signals cannot re-radiate from the active electrode plate(s) 1 76. This is a very important concept. Until the undesirable EMI energy is decoupled to ground, it cannot be left unshielded inside the overall electromagnetically shielded housing of the electronic device or AIMD. If left unshielded, such high frequency noise could cross-couple into sensitive AIMD sense circuits. For example, if a cardiac pacemaker senses such high frequency noise as a heartbeat, the pacemaker could inhibit which could be life-threatening for a pacemaker-dependent patient.
[Para 228] FIGURE 60 illustrates an alternative active electrode layer to that which was previously described as 1 76 in FIG. 58. Referring to FIG. 60, one has to imagine removing the exploded active electrode view layer 1 76 in FIG. 58 and replacing it with the active electrode 1 76'. The active electrode plate 1 76' itself is not much different from that previously illustrated in FIG. 58 (its surface area is slightly smaller). What is different is that a grounded or third shield trace 224 has been deposited around the active electrode 1 76' on the same co- planar surface. The purpose of the surrounding grounded shield trace 224 on the same plane as active electrode 1 76' is to further aid in the coaxial shielding of the active electrode plate 1 76'. When one considers that the active electrode 1 76' is already sandwiched between grounded shield plates 1 94 and 1 94', this means that it is now shielded top, bottom and on both sides. The addition of the optional edge shield 224 prevents edge radiation of high frequency from the shielded three-terminal flat-through EMI/energy dissipating filter 1 90. [Para 229] The filter performance of the flat-through capacitor can be further improved by additional low-pass circuit elements. Referring to FIG. 61 , one can see that the active electrode plate 1 76" has been modified by adding a Wheeler spiral inductor element 1 58. Wheeler spiral inductors are well known in the prior art for a variety of other applications. Wheeler spiral design equations are also readily available. The spiral inductor circuit trace 1 58 adds substantial series inductance to the active electrode plate 1 76" and also increases the flat- through capacitance overlap area (ECA) as well. In Fig. 61 , by also having a wide active electrode plate area 1 76", one also maximizes the parasitic flat- through capacitance as previously described. In other words, the increased total effective overlap area (ECA) between the inductor circuit trace of 1 58 and the active electrode plate 1 76" as they are sandwiched between the two ground shield plates 1 94 and 1 94' greatly increases the flat-through capacitance Cp and Cp'. In the art of EMI filter design, when one places an inductor in series with the circuit along with a capacitance to ground, this is known as an L- section low-pass filter. The schematic for the L-section filter of FIG. 61 is shown in FIGURE 62.
[Para 230] Referring to FIG. 62, one can see the Wheeler inductor spiral 1 58 is in series with the active electrode 1 76" which has in parallel to ground both the flat-through parasitic capacitance Cp, and the MLCC capacitor 142 to form an L-filter. Not shown in FIG. 62 is the fact that the parasitic capacitance Cp is really a distributive element and should be shown throughout the circuit. Accordingly, FIG. 62 should be considered a relatively low frequency model wherein a high frequency model would be of a distributed transmission line. [Para 231 ] FIGURE 63 illustrates a quadpolar filtered feedthrough assembly in accordance with the present invention. It is very similar in construction as previously described for the unipolar device of FIGS. 54, 56 and 58. In FIG. 63, one can see that there are multiple ground electrode shield plates 1 94, 1 94' and 1 94". The associated via holes will be obvious to those skilled in the art. Sandwiched between these ground electrode shield plates are active circuit electrode layers 226 and 228. Flat-through electrode circuits 1 76 and 1 76' are contained on electrode circuit trace layer 226. As previously described, parasitic capacitances or flat-through capacitances are formed due to the ECA overlap area on both sides. The spacing of the ground shields 1 94 and 1 94' is quite important in that they should not be spaced too far apart or high frequency RF leakage could occur due to the electromagnetic interference signals re-radiating from the flat-through electrode plates 1 76 and 1 76' out through the outside edge. This RF leakage was prevented in the unipolar design of FIG. 54 by wrapping the metallization surface 208 around the outside. This can also be accomplished by stitching through a number of conductive filled via holes 230 as shown in FIG. 64. FIG. 64 is a modification of the ground shields 1 94-1 94" of FIG. 63. One can see that there are a plurality of these stitching vias 230 or grounding vias all around the perimeter and even inside. The purpose of these stitching vias 230 is to electrically connect the three (or nj ground shield layers 1 94-1 94" together in a multi-point low inductance configuration. These stitching vias form another very important purpose in that they decrease the effective length when one looks at the side view of this laminated sandwiched structure. It is a common principle in waveguide engineering that the cutoff frequency of a waveguide is dependent upon its geometry. For rectangular waveguides, the length-to-width ratios are very important. By shortening the length, one greatly increases the frequency at which the waveguide could start to pass electromagnetic signals through it. Accordingly, by including many stitching vias 230, one is guaranteed that the sandwiched construction maintains RF shielding as to edge re-radiation integrity up into the 5 to 1 0 GHz region. This is well above the effective filtering frequency required for AIMDs. The upper frequency for AIMDs is defined by experts in the art as 3 GHz. The reason that attenuation above 3 GHz is not required for AIMD EMI filters has to do with the reflection and absorption of body tissues at very short wavelengths. Accordingly, it is generally accepted by the implantable medical device EMC community that electromagnetic filters need to be very effective up to 3 GHz, but not beyond. References for this is made to published ANSI/AAMI standard PC69. [Para 232] Referring once again to FIG. 63, it will be obvious to those skilled in the art that multiple layers n could be stacked up. The reason for this would be two fold. That is, to increase effective capacitance area (ECA) for the flat- through capacitances formed between the active electrode plates 1 76n and the surrounding ground shields 1 94n and also to increase the current handling capability of the active circuit electrode plates by putting additional redundant electrodes in parallel. This would tend to decrease the series resistance of said active circuit electrodes and, at the same time, increase their current and power handling capabilities.
[Para 233] Referring once again to FIG. 64, another purpose for the multiple vias 230 is to increase the mechanical integrity of a flexible hybrid substrate 1 92. By having multiple vias 230 stitching through, it becomes much more unlikely that said structure could delaminate. Another way to accomplish this is shown in FIGURE 65, by the use of slot patterns 232. [Para 234] In FIG. 65, there are multiple slots 232 as shown. These slots can be placed in a number of areas. The slots 232 are generally not filled in the same way that a via hole is filled. However, it does allow the adhesive binder layers to contact through the metalized electrode shield. For example, in a typical polyimide flex cable arrangement, multiple layers of polyimide are laid up with an acrylic binder. In this way, by providing for the slots 232, the acrylic binder can contact the underlying substrate material 234. [Para 235] Referring back to FIG. 65, in the present invention it is preferable to align the slots 232 in the direction of active electrode circuit current flow such that torturous paths are not created for current flow. This also tends to maintain the inductive integrity of the ground plate. By way of example, if the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention were used at the point of lead wire ingress of a cardiac pacemaker, then the active electrodes must be low loss in order to conduct both the pacemaker pacing pulses and also conduct the biologic sensing signals. In other words, a modern cardiac pacemaker actively detects and monitors the electrical activity of the heart. One purpose for low loss active electrodes is as an AIMD battery saving purpose. Some patients are not pacemaker dependent, meaning that they only need to be paced at certain critical times when their heart rate drops too low. Therefore the pacemaker electronic circuits constantly monitor the heart. When a pacing pulse is needed, the pacemaker activates and delivers the pacing pulse through implanted leads to the appropriate cardiac tissue. The stimulation pulse then restores the heart to its natural sinus rhythm. Accordingly, it is very important that the active electrodes, such as those shown in Iayer226 and 228 of FIG. 63, be relatively low loss. That is, the resistivity of the active electrodes should not be so high that pacing pulses or sensing signals are significantly attenuated. [Para 236] FIGURE 66 illustrates a methodology of putting multiple holes 236 in the metalized electrode shield. These multiple holes 236 serve the same purpose as the previously described slots 232 in FIG. 65. [Para 237] FIGURE 67 shows an alternative arrangement for the active electrode layer 226 previously shown in FIG. 63. In FIG. 67, one could imagine that this layer 226' could replace layer 226 in FIG. 63. [Para 238] FIGURE 68 is a graph illustrating attenuation versus frequency comparing the performance of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of FIG. 63 with a prior art feedthrough capacitor and a prior art MLCC. One can see significant differences in the comparison of a conventional feedthrough capacitor with that of an MLCC capacitor and the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. In Fig. 68, the feedthrough capacitor and the MLCC are of equal capacitance value. The capacitance value of the shielded three-terminal flat-through EMI/energy dissipating filter is significantly less. The feedthrough capacitor exhibits a small self-resonant dip shown as SRFi . Feedthrough capacitors are unique in that after they go through this type of transmission line self resonance, they continue to function as a very effective broadband filter. The opposite is true for a prior art MLCC capacitor. The MLCC capacitor actually out performs at its resonant frequency SRF other capacitor technologies, however, at frequencies above its self-resonant frequency SRF, it very rapidly becomes inductive at which point the attenuation decreases versus frequency. This is highly undesirable, as high frequency emitters, such as cell phones, would not be properly attenuated. The flat- through capacitance in the present invention is a parasitic capacitance and it tends to be a relatively low capacitance value. That means that its effective 3 dB point (or point where it starts to become an effective filter) is relatively high in frequency. In this case, the 3 dB point is approximately 1 000 MHz. In accordance with the design of Fig. 63, when one combines the MLCC capacitor response curve with the flat-through parasitic curves (these two capacitances are added in parallel) FIG. 68, illustrates the composite or added response attenuation curve (which for active electrode 1 76 is the addition of all of the capacitive elements in parallel illustrated in FIG. 59 (parasitic inductances Lp are so small in value that they can be ignored). When one compares this solid composite curve with that of a prior art feedthrough capacitor, one sees that the prior art feedthrough capacitor out performs the composite curve at frequencies above 1000 MHz. It will be obvious to those skilled in the art that one way around this would be to increase the capacitance value of the flat- through parasitic capacitor so that it could start performing at a lower frequency. An effective way to increase the capacitance value of the parasitic capacitor is to increase the dielectric constant of the surrounding dielectric materials. Referring back to dielectric substrate layers 226 and 228 of FIG. 63, that would mean, for example, using a high dielectric constant (k) dielectric, such as barium titinate or strontium titinate for the insulative substrate material 234. This would raise the dielectric constant (k) up into the area above 2000. Accordingly, the value of the flat-through capacitance would go up so high that one would not even need to include the MLCC capacitance. Another way to accomplish the same thing and to use lower cost materials would be to use flex cable technology, such as polyimide or Kapton flex as previously described. The problem with this is that the dielectric constant of these materials is relatively low (typically below 10). However, one way to make up for this would be to increase the effective capacitance area in the overlap area of the active electrode plates 1 76 and their surrounding sandwiched ground shields 1 94 and 1 94' (and/or reduce the dielectric thickness, d).
[Para 239] FIGURE 69 is an exploded view of the quadpolar hybrid EMI filter of the present invention that is similar to that previously shown in FIG. 63. In FIG. 69, the circuit layers 226 and 228 of FIG. 63 have been modified to add inductor traces 1 58 - 1 58'". These inductor traces are included as part of and are in series with active electrodes 1 76 - 1 76'". It will be obvious to those skilled in the art that one would most likely select one inductor pattern and stay with that. For example, in electrode plate 1 76, there is a rectangular Wheeler spiral inductor 1 58. In electrode plate 1 76', we have by way of example, an inductor meander 1 58' which can be one of many patterns, including those illustrated in FIGURE 74. In electrode plates 1 76" and 1 76'", we have round Wheeler spiral inductors 1 58" and 1 58'" as shown. Embedding co-planar inductors in series with the active electrodes is virtually a no-cost addition. The reason for this has to do with the manufacturing methods typically employed to produce flex cables or even solid substrates. That is, a solid metal layer is laid over the entire surface by plating or other metal-deposition processes and then resistive materials are laid down by silk-screening or similar processes. Then chemical etchings are used to remove all of the metal except for the desired electrode patterns. Accordingly, once a setup is made, adding inductor elements 1 58 - 1 58'" as shown in FIG. 69 becomes very inexpensive and easy to do. Advantages of adding the inductors as shown in FIG. 69 include making the low-pass EMI filter from a single element into what is known as a dual element L-section low-pass filter. A dual element filter has a steeper attenuation slope and is therefore more efficient. There is another advantage from adding the inductor shapes as shown in FIG. 69. By doing this, one increases the ECA and therefore the parasitic flat-through capacitance at the same time. Therefore one ends up with a very efficient distributive filter consisting of the inductance in series with the active electrode(s) and parasitic capacitances in parallel to ground.
[Para 240] FIGURE 70 is very similar to FIG. 69 except that the active electrode trace layers 226" and 228" have been modified by adding an optional surrounding co-planar ground shield 224. This surrounding ground shield concept to prevent substrate edge re-radiation was previously described in relation to FIG. 60. However, the difference in FIG. 70 is that an optional co- planar ground shield 224' has also been disposed on layers 226" and 228" between each of the active electrode traces 1 76 and 1 76' and also 1 76" and 1 76'". For example, with reference to layer 226" of FIG. 70, one can see a co- planar ground shield 224' that is disposed between circuit traces 1 76 and 1 76'. This would be used in the case where it was important to prevent cross-talk between adjacent circuit traces 1 76 and 1 76'. For example, this might be important in a cochlear implant to keep each digital or analog voice channel that stimulates the auditory nerve free of distorting noise from an adjacent channel. This becomes particularly important when the dielectric layer 226" on which the circuit electrodes 1 76 and 1 76' are deposited, are of high k dielectric materials. The use of high k dielectric materials increases the parasitic capacitance that would occur between circuit electrode layers 1 76 and 1 76'. The presence of a co-planar grounded shield trace 224' prevents the cross-talk between the adjacent circuit traces. This cross-talk shield 224' can be used in conjunction with, as shown in FIG. 70, or without (not shown) with the surrounding edge shield 224. The cross-talk shield 224' also need not be used on all active electrode layers in a particular shielded three-terminal flat- through EMI/energy dissipating filter 1 90, but only in those layers where crosstalk is a concern between adjacent circuits. In other words, the cross-talk shield 224' may be used on layer 226" but not be needed on layer 228". It will be obvious to those skilled in the art that on a particular substrate layer, that the number of circuit active electrodes (and optional cross-talk shields) is not limited to two (such as 1 76 and 1 76' as shown in FIG. 70), but can be of any number, n. [Para 241 ] FIGURE 71 is yet another alternative to the quadpolar shielded three-terminal flat-through EMI/energy dissipating filter 1 90 as previously described in relation to FIG. 70. The difference between FIG. 70 and FIG. 71 is the addition of a feedthrough capacitor 1 32 which is bonded to the hermetic terminal 1 1 2 by way of an insulative adhesive washer 200. Feedthrough capacitors 1 32 are well known in the prior art and provide very effective high frequency filtering. FIG. 71 illustrates that these prior art feedthrough capacitors can be used in combination with the novel shielded three-terminal flat-through EMI/energy dissipating filter technology of the present invention. In a preferred embodiment, the structure as illustrated in FIG. 71 would allow for the elimination of the MLCC capacitors 1 42-142'" as illustrated (or they could be replaced by higher value MLCCs, film chip capacitors, tantalum technology or the like). In other words, there would be sufficient capacitance from the feedthrough capacitor 1 32 in combination with the flat-through capacitances of the hybrid substrate electrodes such that it is unlikely that additional filtering would be required for high frequency (above 1 00 MHz) attenuation. However, if one were to desire extremely low frequency filtering, one could use a monolithic ceramic feedthrough capacitor as illustrated in FIG. 71 along with the shielded three-terminal flat-through EMI/energy dissipating filter technology and surface mounted very high capacitance value tantalum capacitors. This would yield a filter that would be effective from all the way down in the kilohertz frequency range all the way up through 10 GHz. For AIMD applications, this would be very important for filtering for low frequency emitters such as those created from electronic article surveillance (EAS) gates or low frequency RFID readers (in the 1 25 to 1 32 KHz or 1 3.56 MHz range). These EAS gates are the pedestals that a person, including a pacemaker patient, typically encounters when exiting a retail store. These detect tags on articles and goods such as to prevent theft. One common system is manufactured by Sensormatic which operates at 58 kHz. It has been demonstrated through numerous publications that these EAS gates can interfere with pacemakers and ICDs. The present invention as illustrated in FIG. 71 would be effective in attenuating signals at 58 kHz all the way up through cell phone frequencies in the GHz range.
[Para 242] FIGURE 72 is a blown up view of the round Wheeler spirals 1 58" and 1 58'" of FIG. 69.
[Para 243] FIGURE 73 is a square Wheeler spiral which is very similar to the rectangular Wheeler spiral 1 58 previously shown in FIG. 69. [Para 244] FIGURE 74 shows some typical inductor meander shapes 1 58'. It will be obvious to those skilled in the art that any number of different inductor shapes can be easily deposited on the same co-planar substrate layer in series and an integral part of the active electrode plate(s) 1 76 of the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 technology of the present invention.
[Para 245] The advantage of adding additional elements to a low-pass filter is dramatically illustrated by FIGURE 75, which illustrates the attenuation curves for various types of low-pass filters. By way of reference, a typical MLCC capacitor curve is shown. As one can see, the MLCC undesirably goes through a self resonant frequency SRF after which its attenuation declines versus frequency (the MLCC undesirably becomes increasingly inductive). However, for shielded three-terminal flat-through EMI/energy dissipating filter of the present invention, one achieves broadband filter performance all the way up to and including 1 0 GHz. As one can see, a single element or C section filter has an attenuation slope of 20 dB per decade. When one adds a series inductor to this, as shown in the L section filter, the attenuation slope increases to 40 dB per decade. The addition of a third element, which makes the filter into either a π or T section, increases the attenuation slope to 60 dB per decade. Going further, one could have a double L, which is shown as a LLi or an LL2, meaning that the inductor can point either towards the body fluid side or to the device side, has an attenuation slope of 80 dB per decade. One can add any number of elements in this way. For example, a 5-element filter will have 1 00 dB per decade attenuation slope. It will be obvious to those skilled in the art that any number of elements could be used.
[Para 246] Referring once again to FIG. 69, the structure shown has an electrical schematic as shown in on FIG. 62 as an L section circuit. The capacitance of this L section consists of the sum of the parasitic flat-through capacitance Cp which is formed between the active electrode plate 1 76 including the ECA formed from the inductors 1 58, and the opposing grounded shields 1 94 and 1 94'. The MLCC capacitor 1 42 in FIG. 62 represents the capacitors 142-1 42'" surface mounted onto the hybrid substrate 1 92. The MLCC capacitor is effective up to its resonant frequency; however, that is where the flat-through capacitance takes over yielding the relatively smooth curve shown in FIG. 75 for the L section filter. It will be obvious to those skilled in the art that the L section could be reversed. In other words, the inductor spiral could be designed and put on the other side of the capacitor as opposed to towards the body fluid side as presently shown in FIGS. 61 and 62. In addition, it will be obvious to those skilled in the art that multiple inductors could be placed inside of the novel hybrid substrate 1 92 in order to form a "π", "T", "LL" or even a "5" or "n" element device. Accordingly, the present invention includes a new method of constructing prior art low-pass EMI filter circuits that are already well known in the art. In other words, the feedthrough capacitor, the L, the π, the T and LL filters are already well known. However, this is the first time, to the knowledge of the inventors, that a flat-through capacitance has been embedded within grounded shields 1 94 and 1 94'. [Para 247] FIGURE 76 is a family of filter attenuation curves similar to that previously shown in FIG. 68. In FIG. 74, one can see that the 3 dB cutoff point, or the point at which the flat-through (Cp) curve of the shielded three-terminal flat-through EMI/energy dissipating filter starts to become effective, has been moved substantially downward in frequency (to the left). In this case, its 3 dB point is approximately 40 MHz. In addition, since it is now part of an L section filter, its attenuation slope rate has been increased from 20 to 40 dB per decade. In FIG. 76, the referenced feedthrough capacitor curve is unchanged as well as the MLCC curve (these are discrete component comparison curves only). However, the composite curve, which is the addition of the MLCC curve, which is surface mounted to the shielded three-terminal flat-through EMI/energy dissipating filter substrate to the shielded three-terminal flat-through EMI/energy dissipating filter active electrode flat-through curve, is now substantially improved. At all points, the composite curve of the shielded three-terminal flat-through EMI/energy dissipating filter with the surface mounted MLCC(s) out performs (has higher attenuation than) the referenced prior art feedthrough capacitor. In many cases, the amount of improvement is very substantial. For example, at MRI frequencies which are 64 MHz for 1 .5 Tesla machines and 1 28 MHz for 3 Tesla machines, there is an improvement anywhere from 1 0 to over 20 dB. This is very significant and very important to protect an active implantable medical device from interference during an MRI scans.
[Para 248] FIGURE 77 illustrates a bipolar hermetically sealed hybrid substrate filter 1 90 of the present invention.
[Para 249] FIGURE 78 is an exploded view of the internal layers taken along line 78-78 in FIG. 77. One can see that in active electrode plates 1 76 and 1 76', the square Wheeler spirals 1 58 and 1 58' have been greatly enlarged. In order for the grounded shield plates 1 94-1 94" to be proper EMI shields and RF grounds, it is essential that they be properly grounded via electrical connection material 21 0-21 0" to the gold braze ring 1 24 of the ferrule 1 20 of the hermetic seal 1 1 2 as shown in FIG. 77. For AIMDs, ferrule 1 20 is typically of titanium, stainless steel or suitable non-corrosive material. Unfortunately, during manufacturing or over time, titanium can build up undesirable oxides. These oxides can act as an electrical insulator or even a semi-conductor. Attachment of electrical components to this oxide can cause undesirable circuit behavior. In the case of a low-pass EMI filter, this can cause degradation of the EMI filter performance. Therefore, it is essential that a connection be made to a non-oxidizing surface. Fortunately, the presence of gold braze 1 24, as shown in FIG. 77, forms a convenient non-oxidizable surface for such attachment. Attachment to this gold braze is described in U.S. Patents 7,038,900 and 7,31 0,21 6 the contents of which are hereby incorporated by reference. [Para 250] In FIG. 77, one can see that there is an electrical connection material 21 0" that connects between metallization band 222 and the gold braze material 1 24. On the opposite side, there is a similar electrical connection 21 0 that is made between metallization band 222' and the same gold braze material. On the left hand side of the hybrid substrate 1 92, electrical connection material 210' is also connected from metallization band 208 and the same gold braze material 1 24. One can also see this in the exploded view of FIG. 78 by looking at the electrical connections 21 0-210" for the ground shields layers 1 94-1 94". In this case, this is known as a three point ground system which forms an adequate (but not ideal) RF ground for the present invention. The more contact there is between these electrical attachments 21 0-21 0", the better. This is because as one increases the contact area to the grounded shield plates 1 94-1 94" it will reduce the electrical impedance and therefore improve their shielding efficiency, particularly at high frequency.
[Para 251 ] FIGURE 79 is an alternative embodiment showing the hybrid substrate 1 92 of the present invention designed to be inserted partially into the ferrule 1 20 of the hermetic seal assembly 1 1 2 as shown in exploded view. There are convenient wire bond or electrical connection pads 1 39-1 39"" as shown. In this case, 1 39"" would be a ground pad, and pads 1 39-1 39'" would be circuit connections. The MLCC capacitors 1 42-1 42'", as previously described, would connect from the active electrodes plates (not shown) of the shielded three-terminal flat-through EMI/energy dissipating filter through vias internally to internal grounded shield plates (also not shown). As previously described, if enough flat-through parasitic capacitance can be generated within the hybrid substrate 1 92, then the MLCC capacitors 142-1 42'" would not be required. Also shown is an optional embedded Wheeler spiral inductor 1 58. There would be one of these in series with each of the MLCC capacitors 1 42- 1 42'" as previously described. A shield ring 242 is provided so that it will be connected through laser welding, brazing, soldering or the like to the ferrule 1 20. This is important so that electromagnetic interference cannot directly penetrate through the insulator 1 1 8 and re-radiate to the interior of the electronic device (a hermetic insulator forms a hole in the titanium electromagnetic shield housing of a cardiac pacemaker). The shield ring 242 is connected via soldering to via holes to the internal ground shield plates of the shielded three-terminal flat-through EMI/energy dissipating filter structure. Connection pads 240 through 240'" are designed to be electrically connected to lead wires 1 1 4 through 1 1 4 '".
[Para 252] FIGURE 80 is a partially fragmented view taken from FIG. 79. In this case, the leads 1 14" and 1 14"'are typically welded, brazed or soldered 244 and 244' into the lead wire retaining blocks 240" and 240'" as shown. One can also see that there is an optional electrical connection 246 and 246' inside of the flange 1 20 of the hermetic seal 1 1 2. This electrical connection makes contact to the internal grounded shield plates (not shown) of the hybrid substrate 1 92. One can see that the electrical connection material 246 and 246' not only makes contact to the titanium flangel 20, but it also makes intimate contact to the gold braze 1 24 such that there is an oxide free electrical connection in order to guarantee high frequency performance. In FIG. 80, one can see that the external shield ring 242 has been eliminated and replaced by a metallization layer 247. The metallization area 247 forms a circumferential ring over the non-conductive insulator 1 1 8 such that re-radiation of EMI through the hermetic seal 1 1 2 is prevented.
[Para 253] FIGURE 81 is the electrical schematic diagram of the quadpolar hybrid EMI filter of FIGS. 79 and 80. FIG. 81 illustrates an L-section low-pass filter.
[Para 254] FIGURE 82 illustrates an inline hybrid substrate 1 92 of the present invention. In this case, there are internal grounded shield plates (not shown) that have already been well described. There are multiple electrical connection points to the gold braze 1 24 consisting of 210-21 0"". In this case, back-to- back MLCC capacitors 142 and voltage suppression diodes 248 (also known as zener diodes) have been incorporated in parallel. This is best understood by referring to the electrical schematic diagram of the structure shown in FIGURE 83. Starting from the outside of an electronics module of the body fluid side of an AIMD (on the left), one can see that as EMI enters, it first encounters a flat- through capacitance Cp in accordance with the novel through electrodes of the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. Then, as you move to the right in FIG 83, the EMI encounters an inductance Li which is typically from an embedded co-planar Wheeler spiral inductor (not shown) contained within the active electrode plates of the hybrid substrate 1 92. Then it encounters the parallel combination of the MLCC capacitor 1 42 and the high voltage suppression diode 248. Then there can be another inductor (optional) L2 that would be embedded within the hybrid substrate 1 92 and an additional flat-through capacitance Cp' before one reaches the electrical connection pads A through F as illustrated. [Para 255] Referring once again to FIGS. 82 and 83, the inductors, for example inductor Lia and L2a, could be constructed of square, rectangular or a round Wheeler spirals or any of the other meander shapes previously described. FIG. 83 illustrates a very efficient five element low-pass filter. [Para 256] FIGURE 84 illustrates another form of the novel hybrid substrate 1 92 of the present invention. The shielded three-terminal flat-through EMI/energy dissipating filter 1 90 includes a hybrid substrate 1 92 is divided into two sections: 1 92' and 1 92". Section 1 92' is a relatively thin area of flex cable and is therefore very flexible. Section 1 92" can be made of similar or same materials as section 1 92' (or it can be a rigid board or substrate to which flexible section 1 92' is connected), but its thickness is built up until it forms what is known in the art as a section of "rigid" cable. This rigid section 1 92" could be of polyimide, Kapton or other typical flex cable construction. It will also be obvious to those skilled in the art that this could also be a piece of rigid multilayer substrate or circuit board, including any of the ceramics or FR4 board or the like. The flex cable section 1 92' is designed to slip down over the pins 1 14-1 1 4'" of a hermetic seal 1 1 2 of an AIMD or any other electronic device (hermetic or not), such as those typically used in telecommunications, consumer electronics, military or even space applications). The hermetic seal 1 1 2 can be any type of terminal, including non-hermetic terminals or even plastic terminals. The present invention is applicable to any electronic assembly or a point at which any lead wires ingress and egress an electronic assembly, subassembly or housing. The methods of attachment to the terminal pinsl 1 4-1 14'" of the hermetic seal 1 1 2 and to the ground pin 1 96 will be described in connection with subsequent drawings.
[Para 257] Referring now to the rigid section 1 92", one sees that a number of passive or active surface mounted electronic components can be mounted (they can also be embedded which is also well known in the prior art of multilayer substrate design). In this particular case, the hybrid substrate 1 92 of FIG. 84 has been designed with convenient lead wires 204-204'" and 1 96 for easy connection to lands of a circuit board 250 perhaps with an integrated circuit or microchip 252 within the active implantable medical device. The circuit board 250 is not part of the present invention, but is important in that the present invention be capable of connecting and interfacing with it. [Para 258] FIGURE 85 is very similar to FIG. 84 except the diode array Di has been replaced with either a passive or an active RFID chip (RFID). In the preferred embodiment, this would be a low frequency passive RFID chip meaning that it would operate at a frequency that could easily penetrate the titanium electromagnetic shield of a typical AIMD or other EMI shielded electronic device. In a preferred embodiment, the RFID chip would operate in the International Standards Organization band of 1 25 to 1 35 kHz. The RFID chip could be used for a number of different purposes, including identification of the model number, serial number of the AIMD, important patient or implanting physician information and the like. See U.S. Patent Application Publication No. US 2006-021 2096 Al , the contents of which are incorporated herein by reference.
[Para 259] The RFID chip as illustrated in FIG. 85 could be simply mounted but not electrically connected to the active electrodes of the shielded three- terminal flat-through EMI/energy dissipating filter. No electrical connections are required for a passive RFID chip. In other words, when an external interrogator/reader was used, a powerful electromagnetic field would activate an antenna within RFID chip and it would automatically use the received power to turn on its microchip and transmit a return pulse. However, in another embodiment, the RFID chip, as shown in FIG. 85 could be electrically connected to power circuits embedded within the shielded three-terminal flat-through EMI/energy dissipating filter such that it received power from the internal battery of the AIMD. In this case, it would be known as an active RFID chip. With an active (powered) RFID chip, it could embody a much more sensitive receiving circuit and also transmit a much more powerful return pulse. In another embodiment, the RFID chip as shown in FIG. 85 could be used as a wake-up feature for AIMD RF telemetry circuits.
[Para 260] In the past, pacemaker and ICD and neurostimulator telemetry was done by close-coupled magnetic coils. In this older art, it was typical that the AIMD would have a multiple turn wire antenna within the titanium housing of the AIMD. There were even AIMDs that use an external loop antenna of this type. To interrogate or reprogram the AIMD, the physician or other medical practitioners would bring a wand, with a similar antenna embedded in it, very close to the AIMD. For example, for a typical pacemaker application, the telemetry wand would be placed directly over the implant with a wire connected to an external programmer. The medical practitioner would move the wand around until the "sweet-spot" was located. At this time, the external programmer would become active and electrograms and other important information would be displayed. Typically, the wand would be right against the patient's skin surface or at most a couple of centimeters away. In the last few years, distance RF telemetry is becoming increasingly common. In this case, for example for a cardiac pacemaker, there would be a high frequency antenna that would be embedded within the plastic header block of the AIMD (outside the EMI shielded titanium housing). This would communicate with an external RF receiver-transmitter programmer. A typical band for such communication would be in the 402 to 405 MHz (known as the MICS band). Other devices use even higher frequencies for distance RF telemetry. A problem with such distance telemetry circuits is the energy consumption of the receiver circuitry which must be on all the time. There is one methodology which is known in the art as the Zarlink chip. The Zarlink chip uses a higher frequency (in the GHz range) to wake-up the lower frequency RF telemetry circuit. The higher frequency is more efficient; however, the device or chip still consumes an amount of idling energy from the AIMD battery to always be alert for its wake- up call. An alternative of this resides in the present invention where a passive RFID chip is used as a wake-up feature. This RFID can be integrated into the hybrid substrate 1 92 of the present invention (or mounted anywhere else inside or outside the housing of the AIMD). In a preferred embodiment, the external RF programmer can incorporate a low frequency RFID reader which would transmit a signal which would penetrate right through the titanium housing of the AIMD and activate the embedded passive RFID chip. The circuitry of the RFID chip would be connected to the telemetry circuits contained within the AIMD. For an example, in the case of a pacemaker, the external programmer would send the RFID signal as a wake-up call to turn on the telemetry receiving circuits so that the pacemaker could communicate with the external programmer. [Para 261 ] FIGURE 86 is very similar to FIG. 84. In this case, toroidal inductors L3-L3'" have been used to replace the surface mount chip inductors . Chip inductors are low in both their inductance value and their current rating. Chip inductors can be acquired in two main forms: a) with a ferrite core and; b) without a ferrite core. For exposure in magnetic resonance imaging applications, it is usually desirable to eliminate ferrite material as it will saturate due to the main static field of the MR scanner. See U.S. Patent Application Publication No. US 2007-01 1 2398 Al and U.S. Patent No. 7,363,090, the contents of which are incorporated herein. In FIG. 86, one can see that the toroidal inductor L3' does have a ferrite core TC with many turns of wire W wrapped around it. This makes for a very large inductor value. However, as mentioned, in an MRI environment, the inductance would drop to a very low value due to the saturation of the ferrite element TC itself. It is a feature of the present invention that the ferrite element would be selected so that it would not exhibit permanent remnants. That is, once the device was removed from the magnetic resonance (MR) scanner, the magnetic dipoles would return to their scattered state and the inductor would continue to operate as previously intended. The purpose of the toroidal inductors L3-L3'" would be to provide a very high inductance value for a low-pass filter so that its 3 dB cutoff frequency would be very low in frequency (for example, below 1 MHz or even down to 58 kHz for EAS gates). In fact, it will be obvious to those skilled in the art that inductor chips could also be large value wound inductors with powdered iron or ferrite toroidal cores. In an MR scanner, the electromagnetic field environments are quire harsh, but are also well known. For example, for a 1 .5 Tesla scanner, the pulsed RF field is at 64 MHz. Accordingly, the shielded three-terminal flat- through EMI/energy dissipating filter could be designed such that its parasitic flat-through capacitance along with MLCC capacitors C2 would provide sufficient attenuation at 64 MHz so that the AIMD could be free from EMI and be operated safely in an MR scanner. Accordingly, it would not matter that the cores of the toroidal inductors 1 56 saturated and that low frequency filtering is thereby not available during the time of the MR scans. Obviously, a person in an MR scanner is not likely to encounter an EAS gate or RFID reader typically found when exiting retail stores. What is important is that after the patient is removed from the MR scanner is that the toroidal inductors (or chip inductors with ferrite cores or layers) not exhibit permanent remnance and return to their original state so that they will continue to provide effective low frequency filtering against emitters that the patient may find in their every day environment.
[Para 262] FIGURE 87 illustrates the flexibility of section 1 92'. As one can see, it is very easy to bend the entire flex section 1 92' into a right angle. This is important so that the entire assembly can easily fit inside the typical spaces and geometries of active implantable medical devices, including cardiac pacemakers and the like.
[Para 263] FIGURE 88 is an internal sectional diagrammatic view taken of the hybrid substrate 1 92 of FIG. 84. In FIG. 88, one can see that the gold braze 1 24 of the hermetic seal 1 1 2 is shown on the left. An electrical connection BGA is made between internal ground via V to shield plates 1 94 and 1 94' and the gold braze material 1 24. These electrodes/RF shield plates 1 94 and 1 94' extend full width throughout the flexible portion 1 92' and the rigid portion 1 92" as illustrated in accordance with the present invention. Other circumferential via holes V (not shown) are used to provide a low impedance attachment to additional points between ground shield plates 1 94 and 1 94' to the gold braze 1 24 of the hermetic seal as shown. There are also additional ground shields connected by via hole V2 to optional/additional RF shields plates 1 94"-l 94"" as shown. As previously mentioned, it is very important that the electrical connection BGA to the gold braze 1 24 be multi-point connections in such that a very low impedance is achieved so that the ground shields can properly function as a faraday cage shield at high frequencies. [Para 264] Starting from the left and moving along to the right on FIG. 88, we will now follow flat-through capacitor active electrode plate 1 76. On the left side, active electrode plate 1 76 is electrically connected to lead wire 1 1 4 from the hermetic terminal by means of via hole and eyelet Vi . For simplicity, we are only going to trace one of the quadpolar circuits 1 76, although it will be obvious to those skilled in the art that the other three are of similar or identical flat-through capacitor construction techniques described herein. Parasitic flat- through capacitances Cp are formed due to the ECA that is formed along the length of active electrode plate 1 76 which is sandwiched between the opposed grounded shield plates 1 94 and 1 94'. Via holes V2, V3, V4, V5 V6, and Vi3 (and others not shown) are part of a multipoint ground system so that the ground plates 1 94 and 1 94' are kept at the same low impedance shield potential. Going further to the right, one encounters via hole Vx and Vy which connect MLCC 142 in parallel with inductor chip 1 56 forming a novel resonant tank filter for attenuating MRI RF signals and the like as previously described in U.S. Patent No. 7,363,090, and U.S. Patent Application Publication Nos. US 2007- 0288058 Al , US 2008-0071 31 3 Al , US 2008-0049376 Al , US 2008-01 61 886 Al , US 2008-01 32987 Al and US 2008-01 1 6997 Al , the contents of which are incorporated herein by reference. As one can see, this parallel combination of inductor chip 1 56 and chip capacitor 142 form a parallel combination which is electrically in series with active electrode plate 1 76 in accordance with the referenced co-pending patent serial numbers. Having MLCC 1 42 and inductor chip 1 56 placed on opposite sides (top and bottom) of the hybrid substrate 1 92 is just one way to form the parallel resonant combination. For example, if one refers to FIGS. 80, 85 or 87 of U.S. Patent Application Publication No. US 2007- 01 1 2398A1 , any of these novel integrated L-C chips could be used as a single element on top (or the bottom) of hybrid substrate 1 92 that would replace both MLCC 142 and inductor 1 56. It will be obvious to those skilled in the art that the parallel bandstop filter formed by Ci and Li can be placed anywhere in the active electrode circuit of the shielded three-terminal flat-through EMI/energy dissipating filter. In other words, it could be moved further to the right, for example, after L2 or even after L3. It will also be obvious to those skilled in the art that any combination of circuit elements is possible, including placing circuit elements 1 42 and 1 56 in series as an inductor-capacitor (L-C) trap filter anywhere between the active electrode 1 76 and ground 1 94, 1 94'. [Para 265] Referring once again to FIG. 88, active electrode plate 1 76 is then routed through via hole W through inductor l_2 and then back down through via hole Vδ back to active electrode plate 1 76. Active electrode plate 1 76 is then electrically continuous to another via hole Vg which is connected to the right hand termination surface of MLCC capacitor C2. The other termination end of the capacitor C2 is connected through via hole V4 to grounded shield substrates 1 94-1 94'". This makes for a very low impedance RF ground connection for capacitor C2. The active electrode plate 1 76 then continues to via hole Vi 0 and up and to the right through inductor L3 whose other end termination returns through via hole Vn putting L3 in series with active electrode plate 1 76. As previously described, inductors L2 and L3 can be chip inductors, including ferrite chip inductors or they can be toroidal wound inductors or other types of inductors. Active electrode plate 1 76 is then connected through via hole V12 to the right hand side of the high voltage suppression diode array Di . The left hand side of the diode array Di is connected through via hole V13 such that it makes connection with grounded shield plates 1 94-1 94'". Active electrode plate 1 76 then exits to the right from via hole V12 over to via hole Vi4 and then up to wire bond pad 1 38 which is very convenient for connection of lead wire 204 as shown. A ground pad GP on top of the hybrid substrate 1 92 has been provided which connects by via hole Ve to the embedded grounded shield plates 1 94-1 94'". [Para 266] Referring now back to FIG. 84, one can see ground wire 1 96 which has been connected to the bond pad area GB. This is not required for all AIMDs, however, it is a very convenient point for connection of integrated circuit substrate 250 ground circuit trace or traces to the housing of the AIMD via lead 1 96 and then to the ground shield plates 1 94, 1 94' of the hybrid flex shielded three-terminal flat-through EMI/energy dissipating filter. As previously described, the ground shield plates are connected to the gold braze 1 24 of the hermetic seal 1 1 2 which is typically laser welded into the overall titanium housing/can of the AIMD (shown as 300 in FIG. 1 14). The housing can act as an EMI shield, an electrode or an energy dissipation surface. In all cases, a low impedance RF ground is required which is accomplished by the grounded shield plates of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention. Referring back to FIG. 88, one can see that there are a number of parasitic flat-through capacitances Cp that are formed in accordance with the present invention between shield plates 1 94 and 1 94' which surround active electrode plate 1 76 on top and bottom as shown. [Para 267] FIGURE 89 is the schematic diagram of the novel hybrid substrate 1 92 of FIG. 84. For example, tracing one of the quadpolar circuits through, for example the circuit labeled 1 76, point "a" is toward the body fluid side of the lead wire 1 14 that connects from the hermetic seal 1 1 2 shown in FIG. 84. Typically, this would connect through a connector block or directly to a lead system where an electrode would come into contact with body tissue (in a unipolar pace or sense mode, the AIMD housing/can would serve as the return electrode). On the opposite side of the hermetic terminal, we have the same lead wire 1 14 which then connects to the via hole Vi of the flexible hybrid substrate 1 92'. The active electrode plate 1 76 enters the bandstop filter BSF which consists of the parallel inductor Li and MLCC capacitor Ci , one sees that we have now entered the shielded part of the substrate meaning that the entire active electrode plate 1 76 is contained within grounded shield plates 1 94 and 1 94'After exiting the bandstop filter BSF, 1 42,1 56, we then go through inductor L2, and then MLCC capacitor C2 is connected to ground 1 94, 1 94'. MLCC C2 is then connected with inductor L3. After active electrode 1 76 exits inductor L3, it is still shielded/sandwiched within the ground plates 1 94, 1 94' of the hybrid substrate 1 92. We then encounter the transient voltage suppression diode array DA. In this case, the diode array is shown connected to ground and acts as a high voltage suppression device. Diode arrays DA of this type are commonly used in AIMDs. The reason for this has to do with the use of either ICDs or automatic external defibrillators (AEDs). AEDs are now commonly deployed in government buildings, hotels, airplanes, and many other public places. These life saving devices are very important. If a person is unconscious, the AED electrodes are placed on the person's chest. The AED then automatically detects dangerous ventricular arrhythmias (such as ventricular fibrillation) and then an automated high voltage biphasic shock is applied to the electrodes. If the person has an implanted pacemaker (which is often the case) then the implanted leads pick up this high voltage shock that is being used to cardiovert the cardiac tissue. Since the implanted pacemaker is a low voltage device, this high voltage shock can damage sensitive internal circuits of the cardiac pacemaker. Accordingly, diode arrays, incorporating back to back diodes, zener diodes, Transorbs™ or the like are commonly used to short the high voltage spike to ground before it can damage sensitive active electronic circuits (such as integrated circuits, hybrid chips and the like). Since the diode array that's typically used takes up a lot of space on the circuit board, it is a feature of the present invention that it could easily be integrated into the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention to save space by placing it on the interconnect circuit. We then exit the novel hybrid substrate 1 92 of the present invention at point "a"' and make an electrical connection to the IC wire bond pad 1 39 as shown. Another way to think of the schematic diagram shown in FIG. 89 is that what we have is a bandstop filter for suppression of MRI or other powerful single frequency emitters in series with a three element T section filter as previously described in connection with FIG. 73 in series with a high voltage suppression diode. It will be obvious to those skilled in the art that the bandstop filter could be located to the right of the C, L, π, T or η element filter. It could also be placed in combination with L-C trap filter to ground. Accordingly, one can see that a number of components have been assembled into one convenient package.
[Para 268] Referring back to FIG. 84, there are a number of other features of the novel hybrid flex substrate 1 92 that need to be pointed out. One of the features is best described by referring back to FIG. 84 wherein the via holes have an enlarged rectangular portion A, B, C and D for suitable electrical probing or electrical testing. This section allows for a robot or a pogo spring connector to be placed on the pad to facilitate electrical testing, accelerated life testing, burn in, insulation test, dielectric withstanding voltage test or other suitable electrical tests as needed. These tests, often performed at elevated temperatures, are essential to assure the long term reliability of the novel shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. In the opposite (right) end of the rigid part of the substrate 1 92", a similar enlarged pad area(s) 1 39 has been provided for similar electrical contact for test instruments as previously described. For ease of manufacturing, it is also convenient that the entire hybrid flex substrate 1 92 be laid flat as is shown. Being laid flat is particularly suitable to be placed into fixtures for modern robots. These robots are typically fed by tape and reel components or trays which house all of the electronic components. By having the basic hybrid substrate 1 92 laying flat, all of the components can be quickly placed by the robots. Assembly by hand is impractical due to the small size of the surface mounted components. For example, the MLCC chips can be 0201 or smaller which is the size of a grain of pepper (.020 inch by .ol 0 inch). It is then a matter of prior art wave-soldering or equivalent techniques to make the electrical and mechanical connections to all of the components. This is followed up by automated optical inspection, electrical test and even X-ray if needed. [Para 269] Again referring to FIG. 84, so that adequate electromagnetic interference protection will be provided to sensitive AIMD electronics and sense circuits, the inductor l_2 will preferably be of a non-ferrite core and the capacitor C2 would be of sufficient value working in conjunction with flat- through capacitance Cp such that those components alone would provide adequate protection at MRI pulsed frequencies. For example, for 1 .5 Tesla MR scanner, the RF pulsed frequency is 64 MHz. It would be desirable for component Cp, L2 and C2 to have over 40 dB attenuation at 64 MHz to provide adequate protection to device electronics. With the use of a very high value inductor L3, as illustrated in FIG. 86, one can provide a very high degree of (attenuation) immunity to low frequency emitters, such as 58 kHz electronic article surveillance (security) gates that are typically used in retail stores. In addition, one can provide a great deal of immunity to low frequency (LF) RFID readers. These are typically used for automotive keyless entry systems and the like. Since neither RFID readers nor store security gates are present in an MR scan room, it does not matter if inductor L3' does saturate in the MR environment. Accordingly, a novel methodology is provided in the hybrid substrate 1 92 such that certain filter components do not saturate during the MR scan and others do. It will be obvious to those skilled in the art that capacitor elements C2 could be a monolithic ceramic capacitor (MLCC), or a very high value aluminum electrolytic or tantalum capacitor. In other words, for very low frequency filtering, a capacitor of several microfarads could be used with a toroidal wound inductor of several hundred microhenries. This would provide attenuation down to very low frequencies.
[Para 270] In FIG. 89, one can see that l_2 working in combination with C2 and l_3 form what is known in the art as a low-pass "T" filter. Any combination of active or passive circuit elements can be readily adapted to the shielded three- terminal flat-through EMI/energy dissipating filter of the present invention. This includes any of the low-pass filter circuits shown in FIG. 75, and any combinations of L-C traps and/or bandstop filters (BSFs). It is a feature of the present invention that the three terminal flat-through capacitance obtained by sandwiching large surface area through electrodes between surrounding ground plates result in a flat-through capacitance suitable to compensate for the self resonance characteristic (see FIG. 1 8) of prior art (and very low cost) MLCCs and allow them to be used in combination with the shielded three- terminal flat-through EMI/energy dissipating filter of the present invention to achieve a very broadband and effective EMI filter and highly effective energy dissipater.
[Para 271 ] FIGURE 90 is an electrical schematic for one circuit A of FIG. 86. In this case, the T circuit low-pass filter has been replaced with a Pl circuit low- pass filter consisting of C2, L2 and C3. In FIG. 90, the bandstop filter BSF consisting of components Li and Ci acting in parallel, has been replaced by a L- C trap filter consisting of Li and Ci that are wired in series to ground 1 94, 1 94'. It is well known that when L-C series components are in resonance, they ideally form a short circuit at the resonant frequency. This is more thoroughly described in U.S. Patent 6,424,234 the contents of which are incorporated herein. Referring once again to FIG. 90, when one is designing the trap circuit, one has to be very careful of the parallel action of Cp and C2. One has to model the circuit very carefully to make sure that the trap filter functions properly in the presence of these parallel capacitances. It is often desirable, and well known in the art, to isolate the L-C trap filter with a series bandstop filter so that it will not interact with other parallel capacitances. It will be obvious to those skilled in the art that a bandstop filter could be inserted on one or both sides of the trap filter or between multiple trap filters to increase its or their efficacy.
[Para 272] Referring once again to FIG. 90, the use of a trap filter would be particularly advantageous if the AIMD were to be exposed to a magnetic resonance imaging environment. For example, if the system were designed to be used in a 1 .5 Tesla scanner, the trap filter could be designed to be resonant at 64 MHz. This would short out 64 MHz signals to ground (the titanium housing of the AIMD). This would not only provide a great deal of immunity and protection to device electronics, it would also desirably short MR energy to the metallic housing of the AIMD such that it cannot reflect back and cause overheating of the distal electrode tip to tissue interface. Using the housing to dissipate energy is described in U.S. Provisional Patent Application Nos. 61 /1 44,1 02, the contents of which are incorporated herein. [Para 273] Referring once again to FIG. 90, the Pl (π) circuit could consist of an MLCC capacitor C2 which would be very effective at high frequencies. L2 could be a toroidally wound inductor with a ferrite core as previously described as L3' from FIG. 86. C3 could be a high value tantalum capacitor. It would not matter if the Pl circuit was effective while the AIMD was operating in a MR scanner. This is because the L-C trap would be made of components which do not saturate in a magnetic field environment. In other words, inductor Li would be non-ferromagnetic and capacitor Ci would generally be of MLCC construction. Therefore, the EMI filtering immunity for the MR environments would consist entirely of the operation of the trap filter operating in combination with the parasitic capacitance (flat-thru capacitance) of the novel hybrid substrate 1 92 of the present invention. Accordingly, the Pl section filter would be very effective when the patient is outside of MR environments for attenuating low frequency signals and signals throughout the frequency range. In other words, the structure as illustrated in FIG. 90 would perform effective filtering from approximately 30 kHz all the way to 1 0 GHz while outside of an MR environment. While in an MR environment, it would perform effective filtering at selected frequencies of one or more trap filters as shown. Only one trap filter is shown, but it will be obvious to those skilled in the art that any number of trap filters could be placed in parallel in order to short circuit multiple RF frequencies. For example, if one were to want the AIMD to be compatible with both 1 .5 and 3 Tesla scanners, then two trap filters would be required; one resonating at 64 MHz and the other one at 1 28 MHz. Again, as previously stated, the L-C trap filter can each be separated by a series bandstop filter consisting of a capacitor in parallel with an inductor so that the components of each individual trap filter do not interact with each other. [Para 274] Reference is made to U.S. Provisional Patent Application Serial No. 61 /1 44,1 02, which describes a number of other frequency selective circuits that can be used to balance the energy during MRI scanning. The objective is to take as much energy off the implanted lead system and shunt it to the conductive housing of the AIMD which then becomes its own energy dissipating surface. It will be obvious to those skilled in the art that any and all of the schematics that are disclosed in U.S. Provisional Patent Application Serial No. 61 /1 44,1 02 can be embodied in the novel hybrid substrate 1 92 of the present invention.
[Para 275] FIGURE 91 is very similar to FIGS. 84, 85 and FIG. 86. The difference is that a prior art feedthrough capacitor 1 32 is being used in conjunction with the hybrid substrate 1 92 of the present invention. Feedthrough capacitors are well known in the prior art, including U.S. Patent Nos. 4,424,551 ; 5,333,095; 5,905,627; and 6,765,779, the contents all of which are incorporated. Referring once again to FIG. 91 , the feedthrough capacitor 1 32 would provide high frequency filtering generally in the frequency range from 1 00-10,000 MHz. As described for FIG. 86, the other board mounted components could then all involve very high capacitance tantalum or aluminum electrolytic capacitors, or toroidal inductors using high permeability ferrite cores. For example, feedthrough capacitor 1 32 would provide sufficient immunity during an MRI scan such that the other components could all saturate. This would provide a very effective broadband filter operating generally in the frequency range from 1 O kHz all the way to 1 0 MHz. [Para 276] FIGURE 92 illustrates the reverse side of the flexible portion 1 92' of the hybrid flex from FIG. 84. One can see that a robot has dispensed a circular portion of thermal-setting conductive thermal setting adhesive 254. This is designed to align precisely with the gold braze 1 24 of the hermetic terminal 1 1 2 of FIG. 84. Accordingly, the entire substrate can be laid down over the hermetic terminal assembly 1 1 2 and then the thermal-setting conductive material 254 can be cured in an oven, furnace or other equivalent process. This makes a suitable electrical and mechanical connection to the exposed ground shield electrode plate 1 94'. Referring back to FIG. 92, one will see that there are gaps left in the circumferential thermal-setting conductive polymer 254. These gaps are present to allow for a free flow of helium during fine leak detection as previously described. There are also via holes Vi , V2, V3 and V4 which are used to connect to the other internal ground shield plates, including plate 1 94.
[Para 277] FIGURE 93 is a sectional view taken along line 93-93 from FIGS. 84 and 92. One can see the electrical connection formed by thermal-setting conductive adhesive 254 between via hole V3 and the gold braze 1 24, for example. Alternative methods of performing this low impedance RF electrical ground connection to the grounded shield plates 1 94, 1 94' of the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention are illustrated in FIGS. 94 through 97. [Para 278] FIGURE 94 illustrates a methodology of pushing a resistance welding electrode pad 256 onto a flex cable rivet eyelet 258 thereby creating a current flow in which results in an elevated temperature sufficient to reflow a low temperature braze 260 solder or the like to the gold braze material 1 24. [Para 279] FIGURE 95 illustrates an outer pin 262 which has been laser welded to the ferrule 1 20. The minimum number of pins is one, but an optimal number would be four to six to provide suitable RF connection to the internal grounded shield plates 1 94 and 1 94' of the present invention. [Para 280] An alternative method is shown in FIG. 96 wherein a series of counterbores or countersinks 264have been provided in the top of the flange 1 20 such that multiple lead wires 1 96 could be placed along with gold braze rings 266. A high temperature brazing furnace is used to reflow the gold performs 266 and electrically and mechanically attach the pins/leads 1 96 to the ferrule 1 20. In this way, a number of ground pins 1 96 would be sticking up such that open via holes of the flexible portion 1 92' of hybrid substrate 1 92 of the present invention could be laid down and electrically attached to the grounded shield plates 1 94, 1 94'.
[Para 281 ] Another RF ground attach methodology is shown in FIG. 97 whereas the ferrule 1 20 is of a pressed powder metallurgy. In this case, a pedestal pin 268 (4 to 6 or more is the ideal number of pedestals) is formed as part of the powder metallurgy process. In this case, all the materials would be typically of titanium which is ideal for this purpose. Because of the problems with titanium oxide formation, a gold sputtering 270, plating or brazing is placed over the terminal pedestal 268 such that a proper oxide-free electrical connection can be made to the hybrid substrate 1 92 of the present invention.
[Para 282] FIGURE 98 shows a modified version of the flexible portion 1 92' of the flex cable assembly of FIG. 84 with four (or more) via holes VH suitable for placement over any of the embodiments described in FIGS. 95 through 97 for electrical attachments to its grounded shield plates 1 94 and 1 94'.
[Para 283] FIGURE 99 illustrates a cross-section 99-99 from FIG. 93 of yet another embodiment illustrating attachment of the active electrodes of substrate 1 92' over a terminal pin 1 1 4 along with some sort of a weld ring 272 or a braze ring. An electrical connection with weld or solder material 274 is shown.
[Para 284] FIGURE 100 illustrates another methodology wherein the lead wire
1 14 as previously shown in FIG. 84 could be bent over and then a low temperature braze 260 can be formed to an enlarged eyelet 276 of the novel hybrid flex substrate 1 92.
[Para 285] FIGURE 1 01 illustrates a novel laser weld cap 278 with a cut out section 280. The cut out area 280 is formed or cut so the metal cap 278 can slip down over the narrow section 1 92' of the flexible portion of the shielded three-terminal flat-through EMI/energy dissipating filter. The laser weld cap
278 can be a stamped titanium, machined titanium, injection molded titanium or a number of other metals.
[Para 286] FIGURE 1 02 is a combined cross-section taken generally from 102-
1 02 from FIG. 1 01 and also from section 1 02-102 from FIG. 84. However, the hybrid substrate 1 92 has been modified to accommodate the novel laser weld cap 278 as illustrated in FIG. 1 01 . In FIG. 1 02 one can see that the laser weld cap 278 is slipped down such that it comes into close contact with the flange 1 20 of the hermetic terminall 1 2. A continuous or discontinuous laser weld or braze 284 is formed as show. This makes a solid metallurgical and low impedance ground contact to the hermetic flange 1 20 and to the laser weld cap 278. An electrical connection 282 is then made to the ground metallization 1 94 of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90 thereby providing a very low impedance RF ground. One can see in FIG. 1 02 that ground shield plates 1 94 and 1 94' X' are external for the purposes of this illustration; however, they could be internal plates as previously illustrated. [Para 287] FIGURE 103 is applicable to many of the illustrated embodiments of the present invention and simply illustrates a methodology of having a circuit trace Ti or T2 dodge around a via hole V such that it maintains a high surface area (to maximize ECA) and remains in electrical isolation. As one can see, in the upper view circuit trace Ti can be routed in a circular manner all around the via hole or it can simply be routed around the via hole. To maximize flat- through capacitance ECA, the upper trace is the preferred embodiment. [Para 288] FIGURE 104 illustrates an alternative embodiment to FIG. 82 in that it is an octapolar design instead of a quadpolar design. Also, instead of having lead wires for transition to integrated circuit boards, it has wire bond pads 286 for convenient connection of jumper wires to other circuits. [Para 289] FIGURE 105 is very similar to FIG. 1 04 except that it illustrates the methodology of breaking up the flex cable portion 1 92' of the hybrid substrate 1 92 into individual arms/traces for direct electrical connection to other locations, for example to an IC board, within a general electronics module or an AIMD.
[Para 290] FIGURE 106 illustrates an in-line octapolar hermetic or non- hermetic terminal 1 1 2 with a hybrid substrate 1 92 of the present invention exploded away from it, but designed to be mounted to it. One can see that there are a number of MLCC capacitors 142 that are in series with an embedded inductor meander 1 58. Wire bond pads 1 39 are provided at the end for convenient connection of jumper wires to AIMD or other electronic device electrical circuits.
[Para 291 ] FIGURE 107 is a manufacturing production flow chart illustrating a very low cost and a very reliable way to manufacture the present invention. By way of illustration, we will be referring to the particular hybrid substrate 1 92 as previously illustrated in FIG. 84. As previously mentioned, it is highly desirable that during assembly that this substrate 1 92 be laid flat. It can then later be bent into any desired shape as shown in FIG. 87. The first step is to dispense conductive epoxy using a robot to achieve the ring of thermal-setting conductive adhesive 254 as previously described in connection with FIG. 92. This is then assembled into the hermetic seal 1 1 2 and cured at temperatures ranging from 1 50 to 300 degrees centigrade. The electrical chip components are then robot-loaded either from tape and reels or from carrier trays. The chip components can consist of any combination MLCC capacitors 1 42, chip inductors 1 56, diodes 1 54, bandstop filters, L-C trap filters, RFID chips or any other electronic components. These are then run through an automated soldering operation and cleaning operation where they go through an automated optical visual inspection. The electrical inspection is also automated. High reliability screening is then done automatically such as burn in, life testing and the like. Parts are then ready for packaging and shipping. [Para 292] FIGURE 108 illustrates a typical 1 6-lead glass hermetic seal 1 1 2 that would be typically found in a cochlear implant. Also shown is a novel hybrid substrate 1 92 of the present invention, which consists of a rigid section 1 92" and a thin flexible section 1 92'. In this case, the thin flexible section 1 92' has been bent over into a 90 degree angle for convenient attachment to the hermetic seal assembly 1 1 2. A number of MLCC capacitors 142 are shown mounted. Not shown are internal ground shield plates of the present invention. The MLCCs 142 can support two purposes in this application. Some of the MLCCs 1 42 are used in series with the flat-through capacitor active electrodes, which are also known in the art as DC blocking capacitors. This is in order to protect body tissues from excessive electrical stimulation. Also shown are another row of MLCC capacitors 142 which are generally connected to ground to perform EMI filtering in accordance with the present invention. This is better understood by referring to the schematic diagram in FIGURE 1 09. [Para 293] Referring to the body fluid side of FIG. 109, starting with the top schematic, as we enter into the shielded area Sh, we first encounter the flat- through parasitic capacitances Cp that are formed in the present invention between embedded ground shields (not shown) and the particular circuit electrode. We then encounter MLCCA which provides additional low frequency EMI filtering in accordance with the present invention. We then enter MLCCD in series which is a DC blocking capacitor which is placed in series with the circuit trace. Note that since they are both shielded, the order of MLCCAand MLCCD can be reversed without loss of EMI attenuation or body tissue protection. The purpose of series DC blocking capacitor MLCCD is to prevent DC bias from reaching body tissue and possibly causing damage or necrosis. In fact, these DC blocking capacitors are well known in the art and are generally required by regulatory agencies, such as the Federal Food and Drug Administration (FDA). [Para 294] FIGURE 1 1 0 illustrates a 5-terminal pin hermetic seal 1 1 2 of the present invention incorporating four quadpolar lead wires 1 1 4-1 1 4'" which are designed to be connected to leads with electrodes that contact body tissue. Also shown is a fifth pin known as the RF antenna pin 288. RF distance telemetry is becoming very popular for AIMDs. In older devices, it was typical that telemetry was performed through embedded coils within the AIMD. A close coupled coil was brought up close to the skin over the implant which is also known as a telemetry wand. Signals were sent through this close coupled telemetry field in order to interrogate the implanted medical device, perform reprogramming and the like. A problem with this type of telemetry is that in order to effectively couple RF energy through the skin, it had to be very low in frequency (generally below 200 kHz). Because of the low frequency, the data
no transmission rate was quite slow. Since modern implantable medical devices often have over 4000 programmable functions and also store a great deal of data such as ECG wave forms, the slow transmission rate is very frustrating and time consuming for medical personnel. In addition, because of the relatively low coupling efficiency, it is necessary that the wand be placed in very close proximity to the implant. It often takes a little time to find the "sweet spot" so that the one will be able to communicate with the AIMD properly. High frequency RF telemetry consisting of antenna 288 has become very popular is generally accomplished in the 402 MHz (MICS band) or at higher frequencies. Because of the high frequency, energy transmission is very efficient. It is now possible for a doctor sitting at his desk to interrogate a pacemaker patient sitting in a chair across the room. Also because of the high frequency, the transmission data transfer rates are much higher. In other words, this system has much more bandwidth. However, a particular problem with this is that we now have a lead wire 288 that enters the interior of the AIMD which cannot, by definition, be EMI filtered. The presence of broadband EMI filtering would tend to strip off the desirable high frequency telemetry signal. Accordingly, it is important that this unfiltered antenna wire 288 be shielded and routed in such a way that EMI cannot enter into the active implantable medical device and cross-couple to sensitive circuits.
[Para 295] Referring to FIG. I l l , one can see that there is an outer metallic shield assembly 290 formed in an oval (can be any enclosed shape) that surrounds all of the terminal pins 1 14-1 14'". This also provides a convenient
in location for the mounting of the hybrid substrate 1 92 of the present invention. Shown are MLCC capacitors 1 42 connected between the circuit traces and a ground metallization 292. Also shown is a novel lid assembly 294 which is metallic and is used to provide a shielded compartment which completely encapsulates or encloses the RF telemetry pin antenna 288. There is a convenient access port 296 shown which would be suitable for connection of a coaxial cable. The outer termination or shield of the coaxial cable would make electrical and mechanical connection to the ground shield 290. The interior pin of the coaxial cable would enter inside the cavity formed by the lid assembly 294 and make electrical connection to the RF telemetry pin at point 288. After all of this assembly work, the lid 294 would be attached to housing 290 by laser welding, soldering, brazing, conductive adhesives or the like. Another alternative to FIG. 1 1 1 would be to manufacture the cavity underneath the lid 294 sufficiently large to place the required electronic RF module to convert the high frequency RF telemetry signals picked up by the antenna 288 into digital signals. Then these digital signals would be EMI noise free and could be routed through either a connector pin or through the aperture 296. [Para 296] FIGURE 1 1 2 is an alternative embodiment to the structure of FIG. I l l , wherein reversed geometry MLCC's 142 are used to provide high frequency attenuation. In addition, optional ferrite beads 298 are used to further improve high frequency attenuation.
[Para 297] FIGURE 1 1 3 is a manufacturing flow chart that describes an alternative method of manufacturing any of the electronic components of the present invention. Monolithic ceramic capacitor manufacturing is well known in the art. However, a more efficient and cost effective way to do this would be to use thick film technology and lay down the components of the shielded three- terminal flat-through EMI/energy dissipating filter 1 90 all at one time all on one hybrid substrate 1 92. Referring to FIG. 1 1 3, you would first condition the substrate for adhesion of the various dielectric and electrode materials. Then you would print the capacitor dielectric or diode materials through multiple print operations. There is typically a drying operation between each multiple printing operation. This can be done literally in as many times (end times) as required until one reaches the desired capacitance value, inductance value or the like. The thick film component is then typically fired in nitrogen at temperatures ranging from 850 to 950 degrees C. This is then laminated into a substrate structure. The layers are printed and etched to form capacitor electrodes and terminations and this is laminated into a substrate or multilayer board and stacked up using prior art application processes. There are then interconnects using conventional vias or micro-vias to complete the fabrication again using all prior art processes.
[Para 298] The novel hybrid substrate 1 92 of the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention can also be used to mount a variety of sensing circuits to be used in conjunction with external or lead-based sensors. For example, for a cardiac pacemaker application, a number of physiologic sensors could be mounted on the novel substrate, including respiration rate sensors, blood pH sensors, ventricular gradient sensors, cardiac output sensors, pre/post cardiac load sensors, contractility sensors, hemodynamics and pressure monitoring sensors. Such components could also be used in conjunction with blood gas or oxygen sensors.
[Para 299] FIGURE 1 1 4 is an outline drawing of an AIMD such as a cardiac pacemaker. Shown is a metallic, typically titanium, housing 300. It is hermetically sealed with a laser weld 302 as shown. It has a hermetic seal 1 1 2, which is also laser welded to the titanium housing 300. The housing is also hermetically sealed by laser weld 302. The hermetic seal 1 1 2 has an insulator 1 1 8, which is well known in the prior art, through which lead wires 1 14-1 14'" pass through in non-conductive relationship with conductive housing 300. A typical pacemaker connector block 304 is shown. This can be in accordance with various international standards organization (ISO) specifications such as IS-I , DF-I , IS-4 and the like. The female connector block 304 allows for convenient connection of a lead with a male proximal plug(s), which can be routed to the appropriate body tissue to be sensed or stimulated. The lead wires 1 14 through 1 1 4'" are generally routed to circuit boards, hybrid or integrated circuits or substrates 250 within the active implantable medical device housing 300. These can include cardiac sense circuits, pace circuits and the like. There are also variable impedance elements 306 and 308 as illustrated on lead wire 1 1 4'". It should be noted that these variable impedance circuit elements would appear on all of the lead wires 1 14-1 1 4'". They are only shown on lead wire 1 14'" to simplify the drawing. A novel feature is to use the metallic housing of the AIMD as a large surface area energy dissipating surface (EDS). This is also described in U.S. Provisional Patent Application Nos. 61 /1 44,1 02 and 61 /1 49,833, the contents of which are incorporated herein. The shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention is an ideal way to reduce to practice and mount all of the various circuit components as described in U.S. Provisional Patent Application Nos. 61 /1 44,102 and 61 /1 49,833. Typically the AIMD is installed in a pectoral pocket, an abdominal pocket or in some other location that is not in intimate contact with a body organ. Accordingly, if the housing 300 were to overheat, it would be surrounded by fat and muscular tissue which is not nearly as sensitive to thermal damage as, for example, cardiac tissue or brain tissue. Also referring back to FIG. 1 1 4, one can see that for AIMDs, the relative surface area of the housing 300 is quite large in comparison to the electrode tip at the end of an implanted lead. In other words, it embodies a great deal of surface area over which to dissipate the MRI RF energy. Accordingly, the thermal rise will be very low (just a few degrees) as opposed to if the energy were concentrated over a small area in electrode tip where the thermal rise can exceed 30 or even 60 degrees centigrade. Accordingly, it is a feature of the present invention that the housing of the AIMD be used as an energy dissipating surface optionally and ideally working in combination with bandstop filters installed at or near the distal electrode to tissue interface. In FIG. 1 14, this energy dissipation is represented by the arrow marked EDS. In fact, the energy is being dissipated at all points all around the metallic housing 300 to the surrounding body fluids and tissues.
[Para 300] FIGURE 1 1 5 is a close-up view of the variable impedance elements 306 and 308 from FIG. 1 1 4 located within the housing 300 of the AIMD. As previously mentioned, the variable impedance elements 306 and 308 would be installed on all of the leads that ingress and egress the AIMD. The ground symbol g is shown to indicate that variable impedance element 306 is connected through the shielded ground plates of the three-terminal flat- through EMI/energy dissipating filter of the present invention to the metallic housing 300 of the AIMD. The lead wire lengths are not of particular concern since they will be embedded within the novel shielded three-terminal flat- through EMI/energy dissipating filter technology of the present invention. This is very important because each circuit electrode of the present invention is shielded such that a very high amplitude electromagnetic energy from MRI cannot re-radiate or cross-couple over to sensitive AIMD circuits (such as pacemaker sense circuits). The sections of lead wire Si and S2 are kept within the shields 1 94 and 1 94' of the shielded three-terminal flat-through EMI/energy dissipating filter so that high frequency energy from MRI will not be reradiated to sensitive AIMD circuits. Ideally, circuit element 306 would be an MLCC chip 1 42 which would be bonded right at the point of lead wire ingress and egress.
[Para 301 ] FIGURE 1 1 6 illustrates that the variable impedance element 306 of FIG. 1 1 5 can be any type of capacitor (C) element, including MLCC chip capacitors 142 and the like. FIGURE 1 1 7 illustrates that the variable impedance element 306 can also be a feedthrough capacitor C 1 32 as has been noted is in the prior art and illustrated in FIG. 91 .
[Para 302] FIGURE 1 1 8 indicates that variable frequency selective element 306 can also be an inductor (L) in series with a capacitor (C) also known as a L-C trap filter.
[Para 303] FIGURE 1 1 9 illustrates that the trap filter of FIGURE 1 1 8 can be used in combination with either a chip capacitor Cx or equivalent capacitor as previously illustrated in FIGURE 1 1 6 or a feedthrough capacitor as illustrated in FIGURE 1 1 7. For a pacemaker or an ICD, this would be the most common embodiment. Typical capacitance value for the series resonant trap would be 270 nanohenries of inductance and 22 picofarads of capacitance. This would make the series trap filter series resonant at 64 MHz. It's also important that the designer realize that at a certain frequency, the combination of the trap filter 306 and the EMI filter Cx will at some point become a parallel resonant bandstop filter. This happens at frequencies at which the trap filter becomes inductive. In other words, at resonance, the inductive reactance cancels out the capacitive reactance and the impedance of the series trap is essentially zero except for its real or resistive losses. However, at frequencies above resonance, the inductive reactance term tends to increase and dominate the capacitive reactance term. In other words, at frequencies above resonance the series LC trap will tend to look like an inductor which could then cause a secondary resonance in parallel with the feedthrough capacitor Cx. This means that there would be a minor degradation in the overall attenuation to electromagnetic interference. This resonant point should not appear at the frequency of a new and powerful emitter. Resonance at these emitter frequencies therefore should be avoided.
[Para 304] FIGURE 1 20 is essentially the same as FIGURE 1 1 5 except the focus is now on the series variable impedance element 308. The use of a series impedance element 308 is optional, but highly desirable for AMDs that have sense circuits.
[Para 305] FIGURE 1 21 indicates that the variable impedance element 308 can be an inductor L as shown. This forms what is known in the art as a single element low-pass filter. The inductor element L would freely pass low frequencies such as biologic frequencies but would offer a higher impedance to high frequencies such as those of MRI RF pulse frequencies, cellular telephones and the like.
[Para 306] FIGURE 1 22 illustrates that the variable impedance element 308 can be a bandstop filter (BSF) consisting of parallel resonant L-C components as shown. The operation of the bandstop filter has been described in U.S. Patent
Application Publication No. US 2007/01 1 2398 Al , the contents of which are incorporated by reference herein.
[Para 307] FIGURE 1 23 illustrates that the optional series impedance element
308 can be any one of a family of low-pass filters. As previously described in connection with FIGURE 1 21 , this could be a single element low-pass filter consisting of a single inductor element L,26 or a single capacitor element C, 20, 306. This could also be an L filter consisting of an inductor element 308, 26, and a second capacitor 304, 20. Variable reactance frequency selective element 308 could also be a T filter or an n element filter which includes π, LL, five element and the like-type low-pass filters. As one can see from FIGURE 1 23, the attenuation versus frequency slope increases with increasing number of circuit elements. The other desirable effect is by having additional capacitors connected to the housing 300 of the AIMD, one creates additional circuit paths for dissipation of energy to the energy dissipating surface EDS. Accordingly, in the preferred embodiment, one would have one or more a parallel selective frequency element(s) 306 acting in cooperation with one or more series frequency reactive element(s) 308 as illustrated in FIGURES 1 1 5 and 1 20. [Para 308] For a description of prior art feedthrough capacitors, one is referred to U.S. Patent Nos. 4,424,551 or 5,333,095 or 6,765,779, wherein feedthrough capacitors having extremely low inductance are installed at the point of lead wire ingress to an active implantable medical device. For a further description of the L-C trap filter illustrated in FIG. 1 1 7, one is directed to U.S. Patent No. 6,424,234 which illustrates very low inductance (leadless) methods of installing the trap filter at the point of lead wire ingress or egress of the AIMD or at any location in the shielded three-terminal flat-through EMI/energy dissipating filter.
[Para 309] FIGURE 1 24 illustrates a schematic diagram of a series inductor L - capacitor C filter which is commonly known in the industry as an L-C trap filter. The trap filter was previously described in FIG. 1 1 8. Referring once again to FIG. 1 24, there is a particular frequency for a trap filter when the capacitive reactance becomes equal and opposite to the inductive reactance. At this single frequency, the capacitive reactance and the inductive reactance cancel each other out to zero. At this point, all one has left is the parasitic resistance R. If one selects high quality factor (Q) components, meaning that they are very low in resistance, then the trap filter of FIG. 1 24 ideally tends to look like a short circuit at its resonant frequency fr between points A and B which may comprise connections respectively to lead wires 1 1 4-1 14'" which are connected to active electrodes of the shielded three-terminal flat-through EMI/energy dissipating filter 1 90.
[Para 310] FIGURE 1 25 gives the resonant frequency equation where fr, in this case, was measured in hertz. Referring once again to FIG. 1 24, it is very important that the amount of resistance R be controlled. This is better understood by referring to FIGURE 1 26.
[Para 31 1 ] FIGURE 1 26 is a graph that illustrates the impedance Z in ohms versus frequency of the series resonant L-C trap filter of FIG. 1 24. As one can see, the impedance is quite high until one reaches the frequency of resonance fr. At this point, the impedance of the series L-C trap goes very low (nearly zero ohms). For frequencies above or below resonance fr, depending on the selection of component values and their quality factor (Q), the impedance can be as high as 100 to 1 000 or even 1 0,000 ohms or greater. At resonance, the impedance tries to go to zero and is limited only be the amount of parasitic resistance R (FIG. 1 24) that is generally composed of resistance from the inductor L and also the equivalent series resistance that comes primarily from the electrode plates of the capacitor C. There is a trade off in proper selection of the components that controls what is known as the 3 dB bandwidth. If the resistance is extremely small, then the 3 dB bandwidth will be narrower. However, this makes the trap filter more difficult to manufacture. Accordingly, the 3 dB bandwidth and the resistive element R are preferably selected so that it is convenient to manufacture the filter and tune it to, for example, 64 MHz while at the same time providing a very low impedance R at the resonant frequency. For an ideal L-C series resonant trap filter, wherein ideal would mean that the resistance R would be zero, then the impedance at resonance would be zero ohms. However, in this case, the 3 dB bandwidth would be so narrow that it would be nearly impossible to manufacture. Accordingly, some amount of resistance R is in fact desirable.
[Para 312] FIGURE 1 27 is an impedance versus frequency curve wherein two trap filters have been installed which are designed to resonate at two different frequencies. In this case, the first trap filter consisting of capacitor element C and inductor element L, is designed to be self-resonant at the RF pulse frequency of a 1 .5 Tesla MRI system (64 MHz). A second trap filter has been installed in parallel consisting of capacitor element C and inductor element L' with component values designed to be self-resonant or have been designed such that the trap filter is self-resonant at 1 28 MHz (the operating frequency of a 3 Tesla MRI system). Referring once again to FIG. 1 27, one can see an optional bandstop filter BSF consisting of the parallel configuration of inductor Lx and capacitor Cx. The purpose of the bandstop filter is to isolate the two trap filters so that they can work independently. The presence of the bandstop filter prevents secondary resonances from occurring because of the tendency for capacitors C and C to appear in parallel along with inductors L and L' to appear in parallel. In other words, one gets a smoother double trap response when one uses a bandstop filter to electrically isolate the L-C traps into separate components at the frequency of interest. [Para 31 3] FIGURE 1 28 is an overall outline drawing showing a cardiac pacemaker 31 0 with endocardial leads implanted into a human heart 31 4 as shown. Each lead is bipolar meaning that it contains two lead wires. One can see that lead 31 2 is routed into the right atrium and that lead wire 31 2' is routed into the right ventricular apex (RVA). The distal electrodes for the atrial lead are shown at tip 31 6 and ring electrode 31 8. In the right ventricle, the distal electrode tip 31 6' is shown in close proximity to distal ring electrode 31 8'. As previously mentioned, bandstop filters in accordance with U.S. Patent No. 7,363,090 would be placed at or near the distal electrodes 31 6, 31 6' 31 8, 31 8' as needed. Referring to the AIMD housing 31 0, one can see that there are variable impedance elements 306 and 308 associated with each one of the lead wires which can be incorporated into the shielded three-terminal flat-through EMI/energy dissipating filter 1 90.
[Para 314] FIGURE 1 29 is a cross-sectional view of a human head showing a deep brain stimulator electrode 320. Lead wires 31 2 and 31 2' are typically routed down the back of the neck and into the pectoral region and connected to an AIMD (brain neuromodulator). FIG. 1 29 is simply to illustrate that the properties of the present invention are not limited to cardiac pacemakers, but have wide applicability to a wide range of AIMDs as previously described with reference to FIG. 1 . The frequency selective components described in FIG. 1 28 can be integrated into the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention in a housing 320 in the skull burr hole which also supports the deep brain electrodes, or in the AIMD housing as shown in FIG. 1 14.
[Para 31 5] FIGURE 1 30 shows a unipolar lead system 31 2 for an active implantable medical device. A unipolar lead system is shown for simplicity. It will be obvious to those skilled in the art that any number of lead wires 31 2 could be used. In FIG. 1 30, one will see that this system involves an AIMD and housing 300 attached to unipolar lead wire 31 2 to a human heart 31 4. At the distal tip or distal end of lead wire 31 2 is an optional bandstop filter BSF located at or near the stimulation/sense electrode. The optional bandstop filter BSF located near the distal electrode is more thoroughly described in U.S. Patent 7,363,090 the contents of which are incorporated herein. The implanted lead 31 2 has inductive L and resistive R properties along its length. The total inductive reactance of lead 31 2 in ohms is given by the formula +jωL as shown in FIG. 1 30. As mentioned, the bandstop filter BSF may or may not be present. Referring once again to FIG. 1 30, one can see that on the interior of the generally metallic housing 300 of the AIMD there are frequency selective components 306 and 308. These frequency selective elements can consist of various arrangements of capacitors, inductors and resistors or even short circuits as will be more fully described in FIGS. 1 31 though 1 33. [Para 316] FIGURE 1 31 illustrates the lead system of FIG. 1 30 wherein an L-C trap filter 306 has been placed inside of housing 300 in a shielded three- terminal flat-through EMI/energy dissipating filter assembly of the present invention. In this case, Ls and Cs have been designed as an L-C trap filter to be resonant at the pulsed RF frequency of the MRI equipment. Therefore, this forms an RF short to the AIMD housing 300 which becomes an energy dissipating surface EDS of the invention disclosed in U.S. Provisional Patent Application Nos. 61 / 144,1 02; and 61 /1 49,833. It is desirable that the surface area of the AIMD housing 300 be relatively large so that very little temperature rise occurs on surface 300 as the MRI RF energy is being dissipated. [Para 31 7] FIGURE 1 32 is another illustration of the unipolar lead system of FIG. 1 30. In this case, element 306 features a capacitive element C whose capacitive reactance is given by the equation -j/ωC. In a preferred embodiment, the inductive reactance of the implanted lead would first be calculated (modeled) or measured in ohms. Therefore, the value of capacitance could be selected such that the capacitive reactance -j/ωC is equal and opposite in ohms to the inductive reactance of the lead +jωL. In this case, the reactances cancel each other so that one obtains maximal energy transfer to the energy dissipating surface 300,EDS.
[Para 318] FIGURE 1 33 is similar to the unipolar lead system previously described in FIGS. 1 30 and 1 32. In this case, as for FIG. 1 32, the capacitance value C has been selected such that the capacitive reactance will be equal and opposite to the inductive reactance of the implanted lead. However, in this case, the resistances are also balanced. In other words, the resistance R of the implanted lead is equal in value to a discrete resistor Rx placed inside or outside of the housing 300 of the AIMD. Ideally, resistor Rx would be incorporated into the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. In this case, maximum power transfer or energy will be dissipated by this discrete resistance Rx as heat. In a preferred embodiment, a thermally conductive but electrically insulative material will be placed onto the shielded three-terminal flat-through EMI/energy dissipating filter over resistor Rx and to the AIMD housing 300 such that maximum energy transfer from resistor Rx will occur. In fact, in a preferred embodiment, resistor Rx shall have a finned high surface area housing for maximal heat transfer area to the surrounding encapsulant. Referring once again to FIG. 1 33, one can see that energy is radiated and conducted from a discrete resistance element Rx shown as EDS. This energy being dissipated turns to thermal (heat) energy. It is desirable to have a relatively large thermal mass located within housing 300. The AIMD housing 300 then becomes a secondary heat dissipating surface (HDS). This thermal energy will be dissipated over the relatively large surface area 300 into body fluids and tissues that surround the AIMD. For example, in a cardiac pacemaker application, housing 300 would be in a pectoral muscle pocket. [Para 319] Referring back to FIGS. 1 32 and 1 33, it is not necessary that the reactances completely cancel, or in the case of FIG. 1 33, it's not particularly important that the resistances are exactly equal. In fact, there is a tradeoff between EMI filtering of the input capacitance and exact cancellation of the +jωL component lead system. As it turns out, through actual testing, it is really only important that the impedance generally be cancelled in the lead system so that at least the bulk of the excess energy from the MRI RF pulse field will be dissipated to the housing 300 of the AIMD. For example, if one calculates that a 75 picofarad capacitor would exactly cancel the inductive reactance of the lead system, one may instead choose to use a 1 000 picofarad capacitance for the flat-through and MLCCs of the shielded three-terminal flat-through EMI/energy dissipating filter. The 1 000 picofarad total capacitance (Cp + C) would still draw a large amount of MRI RF energy from the lead system to the housing 300. The reason one would do this, is that a 1000 picofarad capacitor would offer much more effective EMI filtering to not only the RF pulse frequency (64 MH2 or 1 .4 Telsa MR system), but also for cell phones and other emitters commonly found in the pace environment.
FIG. 1 34 illustrates filtered connectors 322a-322h that are typically used in the military, aerospace, medical, telecommunication and other industries. In an EMI filtered connector, such as those typically used in aerospace, military, telecommunications and medical applications, it is very difficult to install a feedthrough capacitor type planar array to the connector housing or back shell without causing excessive mechanical stress to the ceramic capacitor. A number of unique mounting schemes are described in the prior art, which are designs that mechanically isolate the feedthrough capacitor while at the same time provide the proper low impedance ground connection and RF shielding properties. This is important because of the mechanical stresses that are induced in a filtered connector. It is problematic to install a relatively brittle ceramic feedthrough capacitor in a filtered connector because of the resulting mismatch in thermal coefficient of expansion of the surrounding materials, and also the significant axial and radial stresses that occur during connector mating.
[Para 320] By definition, connectors come in female and male versions to be mated during cable attach. The EMI filtering is typically done in either the female or the male portion, but usually not both. During the insertion or mating of the connector halves, significant mechanical forces are exerted which can be transmitted to the feedthrough capacitor. In summary, feedthrough capacitors or discrete capacitors in prior art filtered connectors involved very expensive mounting techniques. It is not unusual for the filtered connectors, as illustrated in FIG. 1 34, to cost hundreds or even thousands of dollars each. The present invention, using shielded three-terminal flat-through EMI/energy dissipating filter technology offers equal or even higher performance as compared to filtered connector planar array feedthrough capacitors but at a greatly reduced cost and size advantage. [Para 321 ] With reference to FIGS. 1 35 and 1 36, there is shown a prior art sub D-type filtered connector 324 utilizing a planar array feedthrough capacitor (not shown).
[Para 322] FIGURES 1 37 and 1 38 illustrate other types of very common connectors. In this case, the prior art connectors 326 shown in FIGS. 1 37 and 1 38 are not filtered. In particular, in FIG. 1 37, one can see the exposed connector pins P. It is very common that these pins that protrude into a shielded housing in connection with the mounting of the connector. As one can see, these pins P can easily be connected to the shielded three-terminal flat-through EMI/energy dissipating filter of the present invention. [Para 323] FIGURE 1 39 shows a typical connector assembly 330 with an exploded view of a shielded three-terminal flat-through EMI/energy dissipating filter 1 90 of the present invention. The shielded three-terminal flat-through EMI/energy dissipating filter 1 90 can take any of the forms described in the present invention. For example, FIGURE 141 is taken generally from partial section 1 41 -1 41 from FIG. 1 39. One can see that the shielded three-terminal flat-through EMI/energy dissipating filter embodies an MLCC capacitor C, 306. FIGURE 140 illustrates the connector assembly 330, which can be hermetic or non-hermetic, which has been attached to the shielded three-terminal flat- through EMI/energy dissipating filter 1 90 of the present invention. [Para 324] From the foregoing, it will be appreciated that the shielded three- terminal flat-through EMI/energy dissipating filters 1 90 of the present invention have broad application and may be used with a wide range of connectors, terminals and/or hermetic seals that support lead wires as they ingress/egress into electronic modules or shielded housings. The flat-through EMI/energy dissipating filters 1 90 of the present invention provide three- terminal capacitive filtering while simultaneously providing shielding of circuits and signals passing through the robust high current capability electrodes of the flat-through capacitor. The hybrid substrate 1 92 forming a major component of the energy-dissipating filter 1 90 of the present invention, functions in a very equivalent manner to prior art feedthrough capacitors in that: it's internal ground plates act as a continuous part of the overall electromagnetic shield housing of the electronic device or module to physically block direct entry of high frequency RF energy through the hermetic seal or the equivalent opening for lead wire ingress and egress; and, the flat-through EMI/energy dissipating filter effective shunts undesired high frequency EMI signals off of the lead wire (electrodes) to the overall shield housing where such energy is dissipated in eddy currents resulting in a very small temperature rise. [Para 325] In its most basic form, the shielded three-terminal flat-through EMI/energy dissipating filter comprises an active electrode plate through which a circuit current passes between a first terminal and a second terminal, and a plurality of shield plates substantially enveloping the active electrode plate, wherein the shield plates are collectively coupled to a grounded third terminal. More particularly, the plurality of shield plates include a first shield plate on a first side of the active electrode plate, and a second shield plate on a second side of the active electrode plate opposite the first shield plate. [Para 326] Although several embodiments of the invention have been described in detail for purposes of illustration, various modifications of each may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited, except as by the appended claims.

Claims

What is claimed is:
[Claim 1 ] A shielded three-terminal flat-through EMI/energy dissipating filter, comprising: an active electrode plate through which a circuit current passes between a first terminal and a second terminal; a first shield plate on a first side of the active electrode plate; and a second shield plate on a second side of the active electrode plate opposite the first shield plate; wherein the first and second shield plates are conductively coupled to a grounded third terminal.
[Claim 2] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the active electrode plate is insulated from the shield plates by a dielectric material such that the active electrode plate and the shield plates cooperatively form a flat-through capacitor.
[Claim 3] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 2, including a lead wire extending through at least one of the shield plates in non-conductive relation, the lead wire being conductively coupled to the active electrode plate to form the first terminal.
[Claim 4] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 3, including a plurality of active electrode plates each having a first shield plate on a first side thereof and a second shield plate on a second side thereof opposite the first shield plate, wherein each active electrode plate is insulated from its adjacent shield plates by a dielectric material such that each active electrode plate and its adjacent shield plates cooperatively form a flat-through capacitor.
[Claim 5] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 3, wherein the shield plates are conductively coupled to a common ground.
[Claim 6] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 3, including a plurality of lead wires each extending through at least one of the shield plates in non-conductive relation, where each lead wire is conductively coupled to a respective active electrode plate to form the first terminal for said active electrode plate.
[Claim 7] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 3, including a shielded fixture through which the lead wire extends in non-conductive relation.
[Claim 8] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 7, wherein the fixture comprises an hermetic seal.
[Claim 9] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 3, including an adjacent feedthrough capacitor through which the lead wire extends prior to conductively coupling to the active electrode plate to form the first terminal.
[Claim 10] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , including a conductive pad conductively coupled to the active electrode plate and forming the second terminal.
[Claim 1 1 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 0, wherein the conductive pad comprises a wire bond pad disposed on an exterior surface of a body of dielectric material through which the active electrode plate extends.
[Claim 12] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , including a plurality of co-planar active electrode plates insulated from the shield plates by a dielectric material such that each active electrode plate and the shield plates cooperatively form a flat-through capacitor.
[Claim 13] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 2, wherein at least one of the co-planar active electrode plates comprises an inductor.
[Claim 14] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 2, including a co-planar third shield plate extending between the co-planar active electrode plates.
[Claim 1 5] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , including a lead wire or pin extending through at least one of the shield plates in non-conductive relation, the lead wire or pin conductively coupling to the active electrode plate to form the second terminal.
[Claim 16] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , including a monolithic chip capacitor (MLCC) conductively coupled between the active electrode plate and at least one of the grounded shield plates.
[Claim 17] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , including a third shield plate disposed generally co-planarly with the active electrode plate, wherein the third shield plate is conductively coupled to the grounded third terminal.
[Claim 18] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 7, wherein the third shield plate substantially surrounds the active electrode plate and is disposed between the first and second shield plates.
[Claim 19] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein at least a portion of the active electrode plate comprises an inductor.
[Claim 20] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 9, wherein the inductor comprises a spiral circuit trace.
[Claim 21 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 2, including at least one via hole for conductively coupling the shield plates to one another.
[Claim 22] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 21 , wherein the via holes are disposed about the periphery of the active electrode plate.
[Claim 23] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the surface area of the active electrode plate is maximized to increase parasitic capacitance and minimize resistance to current flow.
[Claim 24] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the active electrode plate is configured to form at least a component of an "L", "π", "T", "LL", "5 element", or an "n" element passive electronic low-pass filter.
[Claim 25] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 24, wherein the active electrode plate is configured to form at least a component of a band stop filter, a diode array, or an RFID chip.
[Claim 26] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 24, wherein the passive electronic device is optimized for use at MRI frequencies.
[Claim 27] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the active electrode plate and the first and second shield plates are disposed generally perpendicular to a lead wire conductively coupled to the active electrode plate to form the first terminal.
[Claim 28] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the active electrode plate and the first and second shield plates are disposed generally parallel to a lead wire conductively coupled to the active electrode plate to form the first terminal.
[Claim 29] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 2, wherein the active electrode plate and the shield plates are at least partially disposed within a hybrid flat-through substrate.
[Claim 30] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 29, wherein the hybrid flat-through substrate includes surface metallization forming the third terminal.
[Claim 31 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 30, wherein the hybrid flat-through substrate is disposed adjacent to a hermetic seal for an implantable medical device such that the surface metallization is conductively coupled to a housing for the implantable medical device.
[Claim 32] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 29, wherein the hybrid flat-through substrate comprises a flex cable section.
[Claim 33] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 32, wherein the flex cable section comprises a polyimide, Kapton or acrylic material.
[Claim 34] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 29, wherein the hybrid flat-through substrate comprises a rigid section.
[Claim 35] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 34, wherein the rigid section comprises a high dielectric constant ceramic, alumina, fiberglass or FR4 material.
[Claim 36] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 34, wherein the rigid section includes at least one passive electronic component conductively coupled to the active electrode plate.
[Claim 37] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 36, wherein the passive electronic component comprises an RFID chip, a capacitor, an inductor, a band stop filter, an L-C trap filter, a diode, or a diode array.
[Claim 38] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 37, wherein the capacitor comprises a monolithic chip capacitor.
[Claim 39] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 37, wherein the inductor comprises a monolithic chip inductor or a toroidal inductor.
[Claim 40] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 32, wherein the flex cable section comprises a plurality of flexible sections.
[Claim 41 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 34, wherein the second terminal of the active electrode plate is conductively coupled to a circuit board.
[Claim 42] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 29, wherein the hybrid flat-through substrate comprises a dielectric material with the active electrode plate imbedded therein, the active electrode plate being conductively coupled to surface metallization for at least one via hole through the substrate, and wherein the shield plates comprise surface metallization applied to exterior surfaces of the hybrid flat-through substrate.
[Claim 43] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 42, including a conductive cap configured to capture the hybrid flat-through substrate and conductively couple the shield plates to a ground.
[Claim 44] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 43, including a hermetic seal for an implantable medical device, the hermetic seal including a conductive ferule to which the conductive cap is conductively attached, at least one lead wire extending through the ferule in non-conductive relation and conductively coupled to the surface metallization of the via hole.
[Claim 45] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein all external components thereof comprise biocompatible materials designed for direct body fluid exposure.
[Claim 46] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 37, wherein the RFID chip includes a wake-up feature for initializing AIMD RF telemetry circuits.
[Claim 47] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , incorporated into a passive component network for an implantable lead of an active implantable medical device (AIMD), comprising:
at least one lead wire having a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at a distal end; an energy dissipative surface disposed adjacent to tissue or within the blood or lymph flow of a patient at a point distant from the electrode; and a diversion circuit associated with the lead wire, for selectively diverting high- frequency energy away from the electrode to said energy dissipative surface for dissipation of said high-frequency energy as heat.
[Claim 48] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the passive component network includes an impeding circuit associated with the diversion circuit, for raising the high- frequency impedance of the lead wire, said impeding circuit being disposed between said diversion circuit and the distal end of said at least one lead wire.
[Claim 49] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 48, wherein the impeding circuit comprises an inductor or a bandstop filter.
[Claim 50] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the at least one lead wire comprises a portion of a probe or a catheter.
[Claim 51 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the energy dissipative surface comprises a sheath, an insulative body, or a thermally conductive element.
[Claim 52] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein said at least one lead wire comprises at least a pair of lead wires each having a length extending between and to a proximal end and a tissue-stimulating or biological-sensing electrode at a distal end.
[Claim 53] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 52, wherein said diversion circuit couples each of said lead wires to said energy dissipative surface.
[Claim 54] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 53, wherein said diversion circuit is coupled between said pair of lead wires.
[Claim 55] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the high-frequency energy comprises an RF pulsed frequency of a magnetic resonance scanner.
[Claim 56] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 55, wherein the high-frequency energy comprises a range of selected RF pulsed frequencies.
[Claim 57] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the diversion circuit comprises a low pass filter.
[Claim 58] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 57, wherein the low pass filter comprises at least one of a C filter, an L filter, a T filter, a Pi filter, an LL filter, a 5-element filter, or an "n" element filter.
[Claim 59] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 47, wherein the diversion circuit comprises at least one series resonant L-C trap filter.
[Claim 60] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 48, wherein the impeding circuit includes a nonlinear circuit element.
[Claim 61 ] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 60, wherein the nonlinear circuit element comprises a diode or a transient voltage suppressor.
[Claim 62] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 61 , wherein the diversion circuit comprises at least one series resonant L-C trap filter.
[Claim 63] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 61 , wherein the impeding circuit comprises an inductor or a bandstop filter.
[Claim 64] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 1 , wherein the effective capacitance area of the active electrode plate and its surrounding grounded shielded plates has been relatively maximized in order to achieve a higher value of a three-terminal flat-through capacitor formed therebetween.
[Claim 65] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 64, wherein the dielectric constant of insulating layers between the active electrode plate and the grounded shield plates has also been substantially raised in order to achieve a higher capacitance value of the three- terminal flat-through capacitor.
[Claim 66] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 64, wherein a thickness of dielectric material separating the active electrode plate and the grounded shielded plates has been relatively minimized in order to achieve a higher capacitance value for the three-terminal flat-through capacitor.
[Claim 67] The shielded three-terminal flat-through EMI/energy dissipating filter of Claim 64, including a number of redundant parallel layers of the active electrode plate and surrounding grounded shield plates in order to increase total capacitance value of the three-terminal flat-through capacitor.
PCT/US2009/037700 2008-03-20 2009-03-19 Shielded three-terminal flat-through emi/energy dissipating filter WO2009117599A2 (en)

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